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Chapter 8 Flashcards

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1
Q

*What is the central dogma of biology?

A

DNA → RNA → Protein

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2
Q

*Do all organisms follow the same central dogma?

A

Yes

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3
Q

*What is DNA’s role in the central dogma?

A

Blueprint (stores genetic information)

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4
Q

*What is RNA’s role?

A

A copy of a DNA segment

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5
Q

*What is the role of proteins?

A

Functional products (do the work of the cell)

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6
Q

*What does copying the entire DNA molecule result in?

A

Reproduction

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7
Q

Gene vs. Gene expression

A

Gene: a segment of DNA that contains instructions for making a protein

Gene expression: The process of using that gene to produce a protein - copying the gene so it can be used to make a protein

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8
Q

*DNA → RNA → Protein means what, in plain terms?

A

Blueprint → copy → function

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9
Q

*Why is genetics important in biology and medicine?

A

Genetic changes alter proteins, which alters cell function and causes disease

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10
Q

*How is cancer related to genetics?

A

Cancer is driven by genetic mutations (and epigenetic changes)

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11
Q

*Give an example of a cancer linked to genetics discussed in lecture.

A

Acute myeloid leukemia (AML)

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12
Q

*What is the approximate fatality rate of AML (as noted)?

A

~40–50%, depending on genetic response

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13
Q

*How do genetic mutations lead to disease (central dogma applied)?

A

Mutated DNA → mutated RNA → mutated protein → disease

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14
Q

*How are mRNA vaccines related to genetics?

A

They use RNA to instruct cells to make specific proteins

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15
Q

*How is genetics used in antibiotic production?

A

Genes are used to produce antibiotics in microorganisms

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16
Q

*How is insulin produced using genetics?

A

Through genetic engineering of microbes to produce human insulin

Chunks: human insulin genes - inserted into microbes (bacteria) - microbes express the gene - human insulin is produced

Scientists insert the human insulin gene into bacteria, and the bacteria express the gene and produce human insulin

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17
Q

*Why is antibiotic resistance a genetic issue?

A

Mutations in the bacterial genome alter targets or pathways

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18
Q

*How are biofilms connected to genetics?

A

Gene expression controls biofilm formation and persistence

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19
Q

*Give an example of a biofilm-forming organism mentioned.

A

Streptococcus mutans

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20
Q

*Where is Streptococcus mutans biofilm commonly found?

A

On teeth and toothbrushes

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21
Q

*Why are recurrent infections often genetically driven?

A

Genetic traits allow organisms to persist, resist treatment, or reform biofilms

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22
Q

*Why does genetics matter across medicine, biotech, and microbiology?

A

Because changes in DNA change proteins, and proteins determine function, disease, and treatment response

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23
Q

*Genetics → proteins → real-world impact examples?

A

Cancer severity (AML)
mRNA vaccines
Antibiotic resistance
Biofilm-driven recurrent infections

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24
Q

*What does DNA stand for?

A

Deoxyribonucleic acid

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25
*What is DNA made of?
Nucleotides
26
*What is the overall shape of DNA?
Double helix
27
*What are the components of a DNA nucleotide?
- sugar (deoxyribose) - phosphate - nitrogenous base
28
*What is complementary base pairing in DNA?
Specific pairing of bases across the two strands
29
*Which bases pair together?
Adenine (A) pairs with Thymine (T) Guanine (G) pairs with Cytosine (C)
30
*How many hydrogen bonds connect A–T?
2 hydrogen bonds
31
*How many hydrogen bonds connect G–C?
3 hydrogen bonds
32
*Which base pair is stronger, A–T or G–C?
G–C (because it has 3 hydrogen bonds)
33
*Why is complementary base pairing important?
It allows accurate DNA replication and transcription
34
*DNA structure in one line?
Double helix made of nucleotides with complementary base pairing (A–T, G–C)
35
*What is a gene?
A segment of DNA that codes for a functional product
36
*Is an entire DNA molecule considered a gene?
No
37
*What determines whether a DNA segment is a gene?
It must code for a functional product
38
*If a DNA segment does not code for a product, is it a gene?
No
39
*What do genes code for directly?
RNA
40
*What are the three main types of RNA genes code for?
mRNA, rRNA, tRNA
41
*Which RNA type eventually leads to protein production?
mRNA
42
*Why are mutations in mRNA especially dangerous?
They lead to faulty proteins
43
*Why do faulty proteins cause problems?
Proteins perform cellular functions — if they’re wrong, function is impaired
44
*Gene vs whole DNA molecule — what’s the difference?
Gene → functional segment DNA molecule → entire genetic blueprint
45
*Define a gene in one sentence.
A gene is a segment of DNA that codes for RNA - then makes a functional product
46
*"Codes for a product" =
gene
47
*"Entire DNA copied" =
reproduction
48
*"Single segment copied" =
gene expression
49
*What is genetics?
The study of genes
50
*When genetics “change,” what is actually changing?
Genes are mutated
51
*What is the direct consequence of a mutated gene?
The functional product is altered
52
*How does a gene mutation lead to disease?
Mutated gene → mutated RNA → mutated protein → disease
53
*Why do mutations often cause disease?
Proteins perform cellular functions altered proteins impair function
54
*Genetics change = what outcome?
Altered genes → altered proteins → altered function
55
*What does antiparallel mean in DNA?
The two DNA strands run in opposite directions
56
*What determines the direction of a DNA strand — the bases or the sugar?
The sugar molecule
57
*Which carbon of the sugar holds the nitrogenous base?
The 1′ (one-prime) carbon
58
*Which carbon of the sugar holds the phosphate group?
The 5′ (five-prime) carbon
59
*In what direction does one DNA strand run?
5′ → 3′
60
*In what direction does the complementary DNA strand run?
3′ → 5′
61
*What do we call this opposite orientation of the two strands?
Antiparallel
62
*Why is antiparallel orientation important for DNA structure?
It allows bases to align properly
63
*What forms between aligned bases?
Hydrogen bonds
64
*What effect do hydrogen bonds have on DNA?
They stabilize the double helix
65
*Why can DNA exist as a stable double helix?
Because antiparallel strands allow optimal hydrogen bonding
66
*Antiparallel DNA in one sentence?
DNA strands run in opposite directions (5′→3′ and 3′→5′), allowing hydrogen bonding and a stable double helix
67
*5′ and 3′ ends
think antiparallel
68
*DNA stability
think hydrogen bonds + antiparallel orientation
69
*What everyday object is used to explain antiparallel DNA?
A zipper
70
*In the zipper analogy, how do the two DNA strands run?
One side runs up The other runs down
71
*Even though the strands run in opposite directions, what still happens?
They connect perfectly
72
*What DNA feature does the zipper teeth represent?
Complementary base pairing
73
*Why is the zipper analogy useful for understanding DNA structure?
It shows how opposite directions still allow stable bonding
74
*Antiparallel DNA using the zipper analogy?
One strand runs up, the other runs down, but they still zip together perfectly
75
*What is the leading strand?
The DNA strand that runs 5′ → 3′
76
*What is the lagging strand?
The DNA strand that runs 3′ → 5′
77
*Why do the terms leading and lagging strand matter?
They are critical for understanding DNA replication
78
*What does it mean that DNA strands are complementary?
Bases pair specifically (A–T, G–C)
79
*What does it mean that DNA strands are antiparallel?
One strand runs 5′ → 3′, the other 3′ → 5′
80
*What determines DNA strand direction?
Sugar orientation (not the bases)
81
*What is a gene?
A segment of DNA
82
*What must a DNA segment do to be considered a gene?
Code for RNA
83
*Why is antiparallel orientation important?
It allows hydrogen bonding between bases
84
*What is the result of hydrogen bonding in DNA?
Hydrogen bonds hold complementary base pairs together, stabilizing the DNA Chunks: Hydrogen bonds between base pairs - hold the two DNA strands together - DNA double helix is stable
85
*Why can DNA exist as a stable double helix?
Because antiparallel strands allow proper hydrogen bonding
86
*What does genetics help explain in medicine?
Disease
87
*How is genetics related to drug resistance?
Mutations alter proteins that drugs target
88
*How is genetics used in biotechnology?
Producing vaccines, insulin, antibiotics
89
*How is genetics related to biofilms?
Gene expression controls biofilm formation and persistence
90
*Summarize DNA structure and genetics in one answer.
- DNA strands are complementary and antiparallel - sugar orientation determines direction - genes are DNA segments that code for RNA - antiparallel allows hydrogen bonding and stability - genetics explains disease, drug resistance, biotechnology, and biofilms
91
*5′ / 3′
think antiparallel
92
*Leading vs lagging
think replication
93
*Mutation
think protein change → disease
94
*What happens when only a portion of DNA is copied?
An RNA molecule is produced
95
*What is RNA ultimately used to make?
Protein
96
*What cellular process connects DNA to protein?
Gene expression
97
*What is the basic structure of DNA?
Double helix
98
*What bases pair together in DNA?
A = T G = C
99
*Which base pair has more hydrogen bonds?
G–C (3 hydrogen bonds)
100
*What is a gene?
A segment of DNA
101
*A gene must code for what to be considered a gene?
A functional product
102
*Does a gene code directly for protein?
No
103
*What do genes code for directly?
RNA
104
*What are the three main RNA types genes can code for?
mRNA rRNA tRNA
105
*Which RNA leads to protein production?
mRNA
106
*What is the role of rRNA?
Forms ribosomes
107
*What is the role of tRNA?
Brings amino acids to build proteins
108
*Is RNA itself the final functional product?
Sometimes — but proteins are usually the final functional outcome
109
*What happens when genes mutate?
Functional products change
110
*How do gene mutations cause disease?
Mutated DNA → mutated RNA → mutated protein → disease
111
*What diseases are commonly linked to DNA mutations?
Cancer (including leukemia)
112
*How are mRNA vaccines related to Chapter 8?
They use RNA to make proteins
113
*How is genetics used in biotechnology?
mRNA vaccines Antibiotic production Insulin production
114
*What is genetics the study of?
Genes
115
*Summarize Chapter 8 in one answer.
Copying part of DNA makes RNA genes are DNA segments that code for RNA RNA leads to protein production mutations alter proteins and cause disease genetics underlies vaccines, antibiotics, and cancer biology
116
*What is the central dogma of genetics?
DNA → RNA → Protein
117
*Do all organisms follow the same central genetics model?
Yes
118
*What is the role of DNA?
Blueprint (stores genetic information)
119
*What happens when a portion of DNA is copied?
RNA is produced
120
*What is RNA used for?
To make a protein
121
*What does copying the entire DNA molecule result in?
Reproduction
122
*What does copying only part of the DNA result in?
Gene expression
123
*Why is the central dogma important in microbiology?
Because microbial traits are determined by genes and proteins
124
*What kinds of microbial traits are explained by proteins and genes?
Virulence factors Antibiotic resistance Biofilm formation Metabolism and growth behavior
125
*Central dogma + microbiology in one sentence?
DNA is copied into RNA to make proteins, and those proteins explain how microbes behave, cause disease, and resist treatment.
126
*How does genetics explain disease?
Mutated DNA → mutated RNA → mutated protein → altered function → disease
127
*Why do mutations cause disease?
Proteins control cell function, and altered proteins malfunction
128
*How is cancer related to genetics?
Cancer results from genetic mutations (often discussed using genomics/epigenetics)
129
*What leukemia example did the professor mention?
Acute myeloid leukemia (AML)
130
*What fatality rate did she associate with AML?
~40–50%, depending on the person’s genetics
131
*Why does genetics matter in AML outcomes?
Genetic differences affect how the disease responds to treatment
132
*What is the genetic basis of antibiotic resistance?
Mutations in the bacterial genome
133
*How do these mutations cause resistance?
They alter proteins that antibiotics target or rely on
134
*Why is antibiotic resistance a genetics problem, not just a drug problem?
Because resistance is inherited through bacterial DNA
135
*How is genetics used in biotechnology?
By controlling DNA to produce specific RNA and proteins
136
*What biotechnology examples were emphasized?
mRNA vaccines, Antibiotic production, Insulin production
137
*What is the unifying concept behind all biotechnology examples?
DNA → RNA → protein
138
*How are biofilms connected to genetics?
Biofilm formation is controlled by gene expression
139
*What everyday biofilm example did she give?
Toothbrush bristles
140
*What organism was mentioned in relation to toothbrush biofilms?
Streptococcus mutans
141
*Why are biofilms linked to re-infection?
Genetic regulation allows biofilms to persist and reform after treatment
142
*What is the professor’s main takeaway about genetics?
All complex ideas (disease, resistance, biotechnology, biofilms) trace back to the simple model: DNA → RNA → protein
143
*Genetics explains what four major areas?
Disease Antibiotic resistance Biotechnology Biofilms
144
*What does DNA stand for?
Deoxyribonucleic acid
145
*What is DNA made of?
Nucleotides
146
*What is the overall structure of DNA?
Double helix
147
*What does complementary base pairing mean?
Bases pair specifically with one another
148
*Which bases pair together in DNA?
Adenine (A) pairs with Thymine (T) = 3 H bonds G pairs with C = 2 H bonds
149
*Which bases pair together in DNA?
Guanine (G) pairs with Cytosine (C)
150
*How many hydrogen bonds form between G–C?
3 hydrogen bonds
151
*How many hydrogen bonds form between A–T?
2 hydrogen bonds
152
*Which base pair is more stable?
G–C (because it has more hydrogen bonds)
153
*Why is complementary base pairing important?
It stabilizes the DNA structure
154
*How does base pairing stabilize DNA?
Hydrogen bonds hold the two strands together
155
*DNA structure summary in one sentence?
DNA is a double helix of nucleotides with complementary base pairing (A–T, G–C) stabilized by hydrogen bonds.
156
*What is a gene?
A segment of DNA that codes for a functional product
157
*Is the entire DNA molecule considered a gene?
No
158
*If a DNA segment does not code for something functional, is it a gene?
No — it is DNA, but not a gene
159
*Why do mutations in genes cause disease?
Because they produce an altered or incorrect functional product
160
*What happens when a gene is mutated?
Mutated gene → altered product → altered cell function → disease
161
*What is the first functional product of a gene?
RNA
162
*Do genes code directly for proteins?
No
163
*What do genes code for directly?
RNA
164
*What are the three main types of RNA genes can code for?
mRNA, rRNA, tRNA
165
*Which RNA type is most dangerous to mutate, according to your prof?
mRNA
166
*Why are mRNA mutations especially serious?
Because they lead to altered proteins
167
*What happens after RNA is made?
RNA is “read off” to make a protein
168
*Why do altered proteins cause problems?
Proteins perform cellular functions — if altered, function is impaired
169
*Gene vs DNA — what’s the difference?*
Gene → DNA segment that codes for RNA DNA molecule → entire genetic blueprint
170
*Define a gene in one sentence, exam-style.
A gene is a segment of DNA that must code for RNA, which leads to a functional product.
171
*If a question says: 'Codes for a product' →
gene
172
*If a question says: 'Altered mRNA' →
altered protein → disease
173
*If a question says: 'Entire DNA copied' →
reproduction (not gene expression)
174
*Besides being complementary, what other key property do DNA strands have?
They are antiparallel
175
*What does antiparallel mean in DNA?
The two DNA strands run in opposite directions
176
*What determines the direction of a DNA strand?
The sugar molecule
177
*Do the nitrogenous bases determine strand direction?
No
178
*Why does the sugar determine antiparallel direction?
Because the sugar has numbered carbons that give DNA directionality
179
*How do complementary and antiparallel properties work together?
Antiparallel orientation allows complementary bases to align correctly
180
*What forms when bases align properly?
Hydrogen bonds
181
*Why is antiparallel orientation important for DNA structure?
It allows stable hydrogen bonding between bases
182
*What is the result of antiparallel orientation and hydrogen bonding?
A stable double helix
183
*Define antiparallel DNA in one sentence.
DNA strands run in opposite directions determined by sugar orientation allowing complementary base pairing and stable hydrogen bonding
184
*DNA strands are always ______ and ______.
Complementary and antiparallel
185
*If a question mentions: Opposite directions, Sugar determines direction, DNA stability
The answer is antiparallel DNA
186
*What part of DNA determines strand direction?
The sugar molecule
187
*Which sugar carbon holds the nitrogenous base?
The 1′ (one-prime) carbon
188
*Which sugar carbon holds the phosphate group?
The 5′ (five-prime) carbon
189
*What does the prime (′) symbol refer to in DNA (e.g., 5′, 3′)?
Sugar carbons
190
*Why is prime notation used instead of just numbers?
To distinguish sugar carbons from base numbering
191
*What happens when the sugar molecule flips orientation?
The direction of the DNA strand changes
192
*How does sugar orientation relate to antiparallel DNA?
Opposite sugar orientations create opposite strand directions
193
*In what direction does one DNA strand run?
5′ → 3′
194
*In what direction does the complementary DNA strand run?
3′ → 5′
195
*What do we call this opposite orientation?
Antiparallel
196
*Why is sugar-based direction important for DNA structure?
It allows complementary bases to align and hydrogen bonds to form
197
*What is the result of correct alignment and bonding?
A stable DNA double helix
198
*DNA strand direction is determined by the ______, not the ______.
Sugar; bases
199
*Summarize sugar carbon numbering and direction in one sentence.
The 1′ carbon holds the nitrogenous base the 5′ carbon holds the phosphate opposite sugar orientations create antiparallel strands running 5′→3′ and 3′→5′.
200
*If a question mentions: Prime symbols (′), 5′ and 3′ ends, Opposite directions
The answer always comes back to sugar carbon orientation.
201
*What happens when the sugar orientation flips in DNA?
The bases come closer together
202
*Why is base proximity important?
It allows hydrogen bonds to form more effectively
203
*What forms between complementary bases when they are aligned properly?
Hydrogen bonds
204
*What effect do hydrogen bonds have on DNA structure?
They increase stability
205
*How did the professor explain antiparallel DNA visually?
When everything “turns,” the bases align closer and bond better
206
*Why does antiparallel orientation make DNA more stable?
Because it optimizes hydrogen bonding between bases
207
*What is the overall result of antiparallel DNA orientation?
Extra structural stability of DNA
208
*Why does antiparallel DNA increase stability?
Flipped sugar orientation brings bases closer together, allowing stronger hydrogen bonding and a stable double helix.
209
*Antiparallel → bases closer → hydrogen bonds → ?
DNA stability
210
*If a question asks “why antiparallel?”, the correct answer always involves:
Base alignment, Hydrogen bonding, Structural stability
211
*Why do leading and lagging strands exist?
Because DNA strands run in opposite (antiparallel) directions
212
*What is the leading strand?
The DNA strand oriented 5′ → 3′
213
*What is the lagging strand?
The DNA strand oriented 3′ → 5′
214
*What DNA property directly causes leading and lagging strands?
Antiparallel orientation
215
*Do leading and lagging strands matter yet for reactions?
Not fully — they become critical in DNA replication
216
*Why does the professor introduce leading vs lagging strands here?
To prepare you for DNA replication concepts later
217
*Fill in the blank: The strand that runs ___ → ___ is the leading strand.
5′ → 3′
218
*Fill in the blank: The strand that runs ___ → ___ is the lagging strand.
3′ → 5′
219
*Leading vs lagging strands in one sentence?
Because DNA is antiparallel, one strand runs 5′→3′ (leading) and the other runs 3′→5′ (lagging), which matters during replication.
220
*If you see: Antiparallel, 5′ and 3′ ends, Replication preview, what should you immediately think?
leading vs lagging strands.
221
What are simple proteins?
Proteins that contain only amino acids.
222
What are conjugated proteins?
Proteins that are combinations of amino acids with other organic or inorganic components.
223
How are conjugated proteins named?
By their non–amino acid component.
224
What do glycoproteins contain?
Sugars.
225
What do nucleoproteins contain?
Nucleic acids.
226
What do lipoproteins contain?
Lipids.
227
What do phosphoproteins contain?
Phosphate groups.
228
What is the role of phosphoproteins in eukaryotic cells?
They are important regulators of activity.
229
Why may bacterial synthesis of phosphoproteins be important?
It may be important for the survival of bacteria such as Legionella pneumophila that grow inside host cells.
230
What two functional groups are in all amino acids?
An amino group and a carboxyl group.
231
What are nucleic acids?
Organic compounds that carry genetic information.
232
Why are nucleic acids called “nucleic”?
Because they were first discovered in the cell nucleus.
233
Which scientists discovered that DNA is the substance of which genes are made?
Oswald Avery, Colin MacLeod, and Maclyn McCarty (1944).
234
What compound did Avery, MacLeod, and McCarty identify as the substance of genes?
Deoxyribonucleic acid (DNA).
235
Who identified the physical structure of DNA?
James Watson and Francis Crick.
236
Whose X-ray information contributed to identifying DNA structure?
Maurice Wilkins and Rosalind Franklin.
237
What additional contribution did Crick suggest about DNA?
The mechanism for DNA replication and how it works as hereditary material.
238
What are the two naturally occurring nucleic acids?
DNA and RNA.
239
What is ribonucleic acid (RNA)?
A nucleic acid that, along with DNA, makes up the nucleic acids.
240
What are the structural units of nucleic acids?
Nucleotides.
241
How many parts does a nucleotide have?
Three parts.
242
What are the three parts of a nucleotide?
A nitrogen-containing BASE A pentose (five-carbon) sugar A phosphate group
243
What sugars can be found in nucleotides?
Deoxyribose or ribose.
244
What elements make up nitrogen-containing bases?
Carbon, hydrogen, oxygen, and nitrogen.
245
What are the nitrogen-containing bases?
Adenine (A), thymine (T), cytosine (C), guanine (G), and uracil (U).
246
Which bases are purines?
Adenine (A) and guanine (G).
247
What is the structure of purines?
Double-ring structures.
248
Which bases are pyrimidines?
Thymine (T), cytosine (C), and uracil (U).
249
What is the structure of pyrimidines?
Single-ring structures.
250
How are nucleotides named?
According to their nitrogen-containing base.
251
What is a thymine nucleotide?
A nucleotide containing thymine.
252
What is an adenine nucleotide?
A nucleotide containing adenine.
253
What is a nucleoside?
A combination of a purine or pyrimidine plus a pentose sugar.
254
What does a nucleoside NOT contain?
A phosphate group.
255
What type of molecule is DNA?
A double-stranded molecule.
256
What does DNA store?
Genetic information.
257
In what cells does DNA store genetic information?
All cells.
258
What are the three components of a nucleotide?
A nitrogen-containing base A pentose sugar A phosphate group
259
What forms the backbone of the DNA double helix?
Alternating sugar and phosphate groups.
260
What shape does the DNA backbone form?
A double helix (twisted ladder).
261
What forms the rungs of the DNA double helix?
Nitrogen-containing bases.
262
What is complementary base pairing?
Pairing of nitrogen-containing bases in DNA.
263
Which bases pair together in DNA?
Adenine with Thymine Guanine with Cytosine
264
Why is understanding DNA structure and function important?
It is essential for understanding: Genetics Recombinant DNA techniques The emergence of antibiotic resistance New diseases
265
What are the key concepts about DNA structure and function?
DNA is a double-stranded molecule that stores genetic information in all cells. A nucleotide consists of a nitrogen-containing base, a pentose sugar, and a phosphate group. Alternating sugar and phosphate groups form the backbone of the double helix; the rungs are formed by nitrogen-containing bases. Complementary base pairing occurs between adenine and thymine, and guanine and cytosine. Understanding DNA structure and function is essential for genetics, recombinant DNA techniques, antibiotic resistance, and new diseases.
266
What forms the backbone of each DNA strand?
Alternating deoxyribose sugar and phosphate groups. The deoxyribose of one nucleotide is joined to the phosphate group of the next.
267
What forms the “rungs” of the DNA double helix?
Nitrogen-containing bases.
268
How do nitrogen-containing bases pair in DNA?
Purine adenine (A) pairs with pyrimidine thymine (T). Purine guanine (G) pairs with pyrimidine cytosine (C).
269
What type of bonds hold DNA base pairs together?
Hydrogen bonds. A–T pairs have two hydrogen bonds. G–C pairs have three hydrogen bonds.
270
Which base is NOT found in DNA?
Uracil (U).
271
Why is the order of bases in DNA important?
The sequence of bases contains the genetic instructions for the organism. Nucleotides form genes. A single DNA molecule may contain thousands of genes. Genes code for protein assembly, determine hereditary traits, and control cellular activities.
272
What is a key consequence of complementary base pairing?
If the sequence of one DNA strand is known, the sequence of the other strand can be determined.
273
What is an example of complementary base pairing?
If one strand is ATGC, the complementary strand is TACG.
274
Why are DNA strands described as complementary?
Because the sequence of one strand determines the sequence of the other.
275
Why is DNA’s structure important for information transfer?
DNA’s unique structure allows accurate transfer of genetic information.
276
How does RNA differ from DNA in structure?
DNA is double-stranded. RNA is usually single-stranded.
277
What sugar is found in RNA nucleotides?
Ribose. Ribose has one more oxygen atom than deoxyribose.
278
Which base is found in RNA instead of thymine?
Uracil (U).
279
Which RNA bases are the same as DNA bases?
Adenine (A) guanine (G) cytosine (C)
280
What are the three major types of RNA?
Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA)
281
What is the role of mRNA, rRNA, and tRNA?
Each has a specific role in protein synthesis.
282
Besides protein synthesis, what other roles does RNA have?
RNA carries genetic codes in some viruses. Some RNA participates in RNA interference (RNAi), which silences or deactivates genes as part of regulatory or defense systems.
283
What is genetics?
Genetics is the science of heredity.
284
What does genetics include the study of?
Genes
285
What does genetics include the study of?
How genes are replicated
286
What does genetics include the study of?
How genes are expressed
287
What does genetics include the study of?
How genes are passed on from one generation to another
288
What does the central dogma of molecular biology describe?
How, typically, DNA is transcribed to messenger RNA.
289
What happens to messenger RNA according to the central dogma?
Messenger RNA is translated into proteins.
290
What is the role of proteins produced through the central dogma?
They carry out vital cellular functions.
291
What effect do mutations have on the central dogma process?
Mutations introduce change into the process.
292
What can mutations ultimately lead to?
New or lost functions.
293
What is genetics?
Genetics is the science of heredity.
294
What does genetics include the study of?
The study of genes: how they carry information, how they replicate and pass to subsequent generations of cells or between organisms, and how the expression of their information determines characteristics.
295
What is the genetic information in a cell called?
The genome.
296
What does a cell’s genome include?
Its chromosomes and plasmids.
297
What are chromosomes?
Structures containing DNA that physically carry hereditary information chromosomes contain the genes
298
What are genes?
Segments of DNA (except in some viruses, where they are made of RNA) that code for functional products.
299
What are the usual functional products of genes?
Proteins, though genes can also code for various types of RNA.
300
What is DNA classified as?
A macromolecule.
301
What repeating units make up DNA?
Nucleotides.
302
What are the three components of a nucleotide?
A nucleobase deoxyribose (a pentose sugar) a phosphate group
303
What nucleobases are found in DNA?
Adenine, thymine, cytosine, and guanine.
304
How does DNA exist structurally inside a cell?
As long strands of nucleotides twisted together in pairs to form a double helix.
305
What forms the backbone of each DNA strand?
Alternating sugar and phosphate groups (the sugar-phosphate backbone).
306
Where are nitrogenous bases located in DNA?
Attached to each sugar in the backbone.
307
What holds the two DNA strands together?
Hydrogen bonds between their nitrogenous bases.
308
How do DNA base pairs always occur?
Adenine pairs with thymine, and cytosine pairs with guanine.
309
What term describes the relationship between the two DNA strands?
Complementary.
310
What does base complementarity mean for DNA sequences?
The base sequence of one DNA strand determines the base sequence of the other strand.
311
What important consequence results from complementary base pairing?
If the sequence of bases of one strand is known, the sequence of the other strand is also known.
312
What example illustrates complementary base pairing?
If one strand has the sequence ATGC, the other strand has the sequence TACG.
313
Why is the transfer of genetic information possible?
Because of DNA’s unique structure.
314
What two primary features of biological information storage does DNA structure explain?
The base sequence stores the actual information Complementary base pairing allows accurate replication
315
How is genetic information encoded in DNA?
By the sequence of bases along a strand of DNA.
316
How is genetic information similar to written language?
Both use a linear sequence of symbols to form meaningful information.
317
How many letters are in the genetic alphabet?
Four (the four kinds of nucleobases).
318
Why can genes store enormous amounts of information using only four bases?
Because 1,000 bases can be arranged in 4¹⁰⁰⁰ different ways.
319
What does the genetic code determine?
How a nucleotide sequence is converted into the amino acid sequence of a protein.
320
What is RNA?
The second principal kind of nucleic acid.
321
How does RNA differ from DNA in strand structure?
DNA is double-stranded RNA is usually single-stranded
322
What sugar is found in RNA nucleotides?
Ribose.
323
How does ribose differ from deoxyribose?
Ribose has one more oxygen atom.
324
Which base in RNA replaces thymine?
Uracil (U).
325
Which bases are shared between DNA and RNA?
Adenine, guanine, and cytosine.
326
What are the three major kinds of RNA in cells?
Messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).
327
What do mRNA, rRNA, and tRNA have in common functionally?
Each has a specific role in protein synthesis.
328
What additional role can RNA have in some viruses?
It serves as the carrier of genetic codes.
329
What is RNA interference (RNAi)?
A process in which genes are silenced or deactivated as part of regulatory or defense systems.
330
What is the central dogma of molecular biology?
DNA is transcribed to messenger RNA, which is translated into proteins that carry out vital cellular functions.
331
How do mutations affect the central dogma?
Mutations introduce change into the process, potentially leading to new or lost functions.
332
What does the complementary structure of DNA allow during cell division?
Precise duplication of DNA.
333
What does each offspring cell receive during DNA replication?
One original strand from the parent.
334
Why does each offspring cell receiving one original strand matter?
It ensures one strand that functions correctly.
335
What is much of cellular metabolism concerned with?
Translating the genetic message of genes into specific proteins.
336
What is a gene usually copied into before a protein is made?
Messenger RNA (mRNA).
337
What ultimately results from making mRNA?
The formation of a protein.
338
When do we say a gene has been expressed?
When the final molecule it encodes (such as a protein) has been produced.
339
How does genetic information flow in cells?
DNA → RNA → Protein.
340
What is this flow of genetic information called?
The central dogma.
341
Who named the central dogma and when?
Francis Crick, 1956.
342
What did Francis Crick propose about DNA and proteins?
The sequence of nucleotides in DNA determines the sequence of amino acids in a protein.
343
What is a genotype?
An organism’s genetic makeup — all its DNA.
344
What does the genotype code for?
All the particular characteristics of the organism.
345
What does the genotype represent?
Potential properties, not the properties themselves.
346
What is a phenotype?
- Actual, expressed properties of an organism - What you actually see - Ex. Brown eyes, curly hair, blood type
347
Give an example of a phenotype mentioned in the text.
An organism’s ability to perform a particular chemical reaction.
348
How are genotype and phenotype related?
Phenotype is the manifestation of genotype.
349
Example: What does E. coli with the stx gene produce?
The stx (Shiga toxin) protein.
350
How are gene names written compared to protein names?
Gene names are italicized; protein names are not
351
What is an organism’s phenotype closely related to at the molecular level?
An organism’s phenotype is closely related to its collection of proteins.
352
Why are proteins central to most cellular properties?
Because most of a cell’s properties derive from the structures and functions of proteins.
353
What are the two main functional categories of proteins in microbes?
Enzymatic proteins – catalyze reaction, chemical reactions, speed up chemical reactions in the cell Structural proteins – form cellular structures, building parts of the cell, form structures or components of the microbe
354
How do phenotypes dependent on lipids or polysaccharides still relate to proteins?
They rely indirectly on proteins because enzymes synthesize, process, and degrade those macromolecules.
355
Why is it a useful simplification to say phenotypes are due to proteins?
Because even non-protein structures ultimately depend on protein activity.
356
What type of chromosome do bacteria typically have?
A single circular chromosome.
357
What is a bacterial chromosome composed of?
A single circular molecule of DNA with associated proteins.
358
How is the bacterial chromosome physically arranged in the cell?
It is looped, folded, and attached at one or several points to the plasma membrane.
359
Approximately how many base pairs are in the DNA of E. coli?
About 4.6 million base pairs.
360
How long is E. coli DNA compared to the size of the cell?
About 1 mm long, which is ~1000 times longer than a 1-µm cell.
361
Why does the bacterial chromosome occupy only ~10% of the cell’s volume?
Because the DNA is twisted, or supercoiled.
362
Does the genome consist entirely of back-to-back genes?
No.
363
What are short tandem repeats (STRs)?
Noncoding regions consisting of repeating sequences of 2–5 base pairs.
364
Where are STRs found?
In most genomes, including E. coli.
365
What are STRs used for?
Diagnosing genetic diseases and paternity testing.
366
What do new technologies allow regarding chromosomes?
Rapid determination of complete base sequences.
367
What are open reading frames (ORFs)?
Regions of DNA likely to encode a protein.
368
Where are open reading frames located within DNA?
Between start and stop codons.
369
What is genomics?
The sequencing and molecular characterization of genomes.
370
What real-world application of genomics is mentioned?
Tracking the Zika virus (described in a Clinical Focus box).
371
What does DNA replication make possible?
The flow of genetic information from one generation to the next.
372
What is the transfer of genetic information from one generation to the next called?
Vertical gene transfer.
373
When does DNA replication occur in relation to cell division?
DNA replicates before cell division.
374
What does each offspring cell receive after DNA replication and cell division?
A chromosome identical to the parent’s.
375
Besides replication, how else does genetic information flow within a metabolizing cell?
DNA is transcribed into mRNA and then translated into protein.
376
What two processes convert genetic information from DNA into protein?
Transcription and translation.
377
What is DNA replication?
One parental double-stranded DNA molecule is converted into two identical DNA molecules.
378
What makes DNA replication possible?
The complementary structure of nitrogenous base sequences.
379
Why can one DNA strand act as a template?
Because the two strands of double-helical DNA are complementary.
380
What happens when replication begins to DNA supercoiling?
Supercoiling is relaxed by topoisomerase (or gyrase).
381
What enzyme unwinds the parental DNA strands?
Helicase
382
What does helicase do?
Unwinds and separates the two parental DNA strands one small segment at a time.
383
Where do new nucleotides come from during replication?
Free nucleotides present in the cell cytoplasm.
384
How do nucleotides pair during replication?
They match exposed bases on the single-stranded parental DNA: Thymine → Adenine Guanine → Cytosine
385
What happens to improperly base-paired nucleotides?
They are removed and replaced by replication enzymes.
386
What enzyme joins new nucleotides to the growing DNA strand?
DNA polymerase
387
What can DNA polymerase NOT do?
It cannot initiate DNA synthesis.
388
What is required before DNA polymerase can add nucleotides?
An already existing, base-paired chain.
389
What enzyme starts DNA synthesis?
Primase
390
What does primase do?
Produces a short RNA primer used to start DNA replication
391
What happens to the RNA primer?
It is destroyed by DNA polymerase.
392
Where does the new DNA strand begin synthesis?
From the end of the RNA primer.
393
What is the replication fork?
The point at which replication occurs as the parental DNA is unwound.
394
As the replication fork moves along parental DNA, what happens to each unwound strand?
Each unwound single strand combines with new nucleotides.
395
What happens after a new complementary strand is synthesized during replication?
The original strand and the newly synthesized complementary strand rewind.
396
Why is DNA replication called semiconservative replication?
Each new double-stranded DNA molecule contains one original (conserved) strand and one new strand.
397
Before studying DNA replication in detail, what concept must be understood about DNA structure?
Paired DNA strands are oriented in opposite directions (antiparallel) relative to each other.
398
How are the carbon atoms of the sugar component of a nucleotide numbered?
They are numbered 1′ (pronounced “one prime”) to 5′.
399
Why are the sugar components of paired DNA strands oriented upside down relative to each other?
So the paired bases can be next to each other.
400
What defines the 3′ end of a DNA strand?
The end with the hydroxyl attached to the 3′ carbon.
401
What defines the 5′ end of a DNA strand?
The end with a phosphate attached to the 5′ carbon.
402
How do the directions of the two DNA strands compare?
The 5′ → 3′ direction of one strand runs counter to the 5′ → 3′ direction of the other strand.
403
Why does DNA structure affect the replication process?
DNA polymerases can add new nucleotides only to the 3′ end.
404
As the replication fork moves along parental DNA, how do the two new strands grow?
They must grow in different directions.
405
What is the leading strand?
The new DNA strand that is synthesized continuously in the 5′ → 3′ direction from a template parental strand running 3′ → 5′.
406
How is the lagging strand synthesized?
Discontinuously in fragments of about 1000 nucleotides.
407
What are the fragments of the lagging strand called?
Okazaki fragments.
408
What must happen to Okazaki fragments after synthesis?
They must be joined later to make the continuous strand.
409
Why does DNA replication require energy?
DNA replication requires a great deal of energy to add nucleotides and form new bonds in the DNA strand.
410
Where is the energy for DNA replication supplied from?
From nucleotides, which are actually nucleoside triphosphates.
411
What is the difference between ATP and the adenine nucleotide in DNA?
The difference is the sugar component.
412
What sugar is found in nucleosides used to synthesize DNA?
Deoxyribose.
413
What sugar is found in nucleoside triphosphates used to synthesize RNA?
Ribose.
414
What happens to phosphate groups when a nucleotide is added to a growing DNA strand?
Two phosphate groups are removed.
415
Why does removing phosphate groups provide energy?
Breaking the phosphate band (hydrolysis) releases energy, which is used to form new bonds in the DNA strand
416
How does DNA replication occur in some bacteria such as E. coli?
DNA replication goes bidirectionally around the chromosome.
417
What does bidirectional replication mean in bacteria?
Two replication forks move in opposite directions away from the origin of replication.
418
Why do replication forks eventually meet in bacterial DNA replication?
Because the bacterial chromosome is a closed loop.
419
What enzyme separates the two DNA loops after replication is completed?
A topoisomerase.
420
What cellular structure is associated with the origin of replication in bacteria?
The bacterial plasma membrane.
421
What happens after DNA duplication if each origin binds to the membrane at opposite poles?
As the cell grows - the DNA copies move apart - ensuring each daughter cells receives one DNA molecule
422
What does each offspring cell receive after bacterial DNA replication is complete?
One complete chromosome.
423
What is the origin of replication?
The site on the chromosome where DNA replication begins.
424
How accurate is DNA replication?
About 1 mistake per 10 billion bases incorporated.
425
What mainly accounts for the high accuracy of DNA replication?
The proofreading ability of DNA polymerase.
426
What does DNA polymerase do during proofreading?
It checks whether each new base forms the correct complementary base pair.
427
What happens if DNA polymerase adds an incorrect base?
DNA polymerase removes the incorrect base and replaces it with the correct one
428
What happens to mismatched bases that escape proofreading?
They are corrected by mismatch repair.
429
What occurs during mismatch repair?
A nuclease removes incorrect bases, and the gap is filled by DNA polymerase and DNA ligase.
430
What is the result of proofreading plus mismatch repair?
Newly synthesized chromosomes are virtually identical to the parental DNA.
431
What problem puzzled biologists about mismatch repair?
How cells distinguish the incorrect base from the correct one.
432
Who helped explain how incorrect bases are identified, and when?
Hamilton Smith, in 1970.
433
What are methylases?
Enzymes that add methyl groups to selected bases shortly after DNA synthesis.
434
How do methylases help mismatch repair?
They mark the old (parental) strand, allowing repair enzymes to target the new, non-methylated strand.
435
Which strand is cut during mismatch repair?
The new, non-methylated DNA strand.
436
How is information in DNA used to make proteins that control cell activities?
DNA information is transcribed into RNA, and the RNA is then used to synthesize proteins through translation.
437
What is transcription?
Transcription is the process where DNA is copied into mRNA Transcription = DNA to mRNA Transcription = DNA to mRNA Translation = mRNA to Protein
438
What happens after transcription?
The cell uses the information encoded in RNA to synthesize specific proteins through translation.
439
Where do transcription and translation occur in this chapter’s focus?
They are examined as they occur in a bacterial (prokaryotic) cell.
440
What is transcription in prokaryotes specifically defined as?
- making mRNA from DNA acts - DNA acts as a template, and RNA polymerase builds a matching RNA strand - the synthesis of mRNA from a DNA template Transcription = DNA to RNA Translation = RNA to protein
441
What is the role of newly synthesized mRNA?
It carries the coded information for making a specific protein to ribosomes, where proteins are synthesized.
442
Which type of transcription is discussed here?
Transcription in prokaryotic cells (eukaryotic transcription is discussed later).
443
What is ribosomal RNA (rRNA)?
rRNA is RNA that forms part of the ribosome, the structure responsible for protein synthesis
444
What is transfer RNA (tRNA)?
Transfer RNA (tRNA) is also involved in protein synthesis.
445
During transcription, what is used as a template?
A specific portion of the cell’s DNA serves as the template for mRNA synthesis.
446
What happens to genetic information during transcription?
The genetic information in DNA is copied into mRNA, keeping the same instructions
447
What is the role of DNA in the cell?
DNA is the blueprint for a cell’s proteins, including enzymes.
448
How is DNA obtained by a cell?
DNA is obtained either from another cell in the same generation or from a parent cell during cell division.
449
How can DNA be used or transferred between cells?
DNA can be expressed within a cell or transferred to another cell through recombination and replication.
450
What happens during DNA replication?
One parental double-stranded DNA molecule is converted into two identical DNA molecules.
451
What feature of DNA is key to understanding DNA replication?
The complementary structure of the nitrogenous base sequences.
452
Why can one DNA strand act as a template during replication?
Because the bases along the two strands of double-helical DNA are complementary.
453
What cellular components are required for DNA replication?
Several cellular proteins (enzymes) that direct a particular sequence of events.
454
What enzyme relaxes supercoiling at the start of DNA replication?
Topoisomerase or gyrase.
455
What enzyme unwinds and separates parental DNA strands?
Helicase.
456
How are new nucleotides added during DNA replication?
Free nucleotides pair with complementary bases on the exposed DNA strand A pairs with T G pairs with C
457
How do bases pair during DNA replication?
T pairs with A G pairs with C
458
What happens to improperly paired bases during replication?
They are removed and replaced by replication enzymes.
459
Which enzyme joins newly added nucleotides to the growing DNA strand?
DNA polymerase.
460
Why can’t DNA polymerase initiate DNA synthesis?
It can only add nucleotides to the end of an already existing, base-paired chain.
461
What enzyme creates the starting point for DNA synthesis?
Primase.
462
What does primase synthesize?
A short RNA primer that allows DNA polymerase to start DNA replication Primate = RNA primer - start replication
463
What happens to the RNA primer?
It is destroyed by DNA polymerase and replaced with DNA.
464
What is the replication fork?
The point at which replication occurs as parental DNA unwinds.
465
Why is DNA replication called semiconservative?
Because each new DNA molecule contains one original and strand and one newly synthesized strand Semi = half old, half new
466
How are paired DNA strands oriented relative to each other?
They are antiparallel (oriented in opposite directions).
467
How are the carbons of DNA sugar numbered?
From 1′ (“one prime”) to 5′.
468
What defines the 3′ end of a DNA strand?
The hydroxyl group attached to the 3′ carbon.
469
What defines the 5′ end of a DNA strand?
The phosphate group attached to the 5′ carbon.
470
How do the two DNA strands run relative to each other?
One strand runs 5′ → 3′ and the other runs 3′ → 5′.
471
Why does DNA structure affect replication direction?
DNA polymerases can add nucleotides only to the 3′ end.
472
What is the leading strand?
The strand synthesized continuously in the 5′ → 3′ direction.
473
What is the lagging strand?
The strand synthesized discontinuously in fragments.
474
What are Okazaki fragments?
Short DNA fragments formed on the lagging strand during DNA replication
475
How are Okazaki fragments joined?
By DNA ligase.
476
Where does the energy for DNA replication come from?
From nucleoside triphosphates.
477
What sugar is used in DNA nucleotides?
Deoxyribose.
478
What sugar is used in RNA nucleotides?
Ribose.
479
How is energy released to form DNA bonds?
Two phosphate groups are removed, and hydrolysis provides energy.
480
How does DNA replication occur in bacteria like E. coli?
Bidirectionally around the chromosome.
481
Why do replication forks eventually meet in bacteria?
Because the bacterial chromosome is a closed loop.
482
What enzyme separates the two replicated DNA loops?
Topoisomerase
483
How does DNA segregation occur in bacteria after replication?
Each copy of the origin binds to opposite poles of the membrane.
484
How accurate is DNA replication?
About 1 mistake per 10 billion bases.
485
What enzyme provides proofreading during replication?
DNA polymerase.
486
What happens if proofreading fails?
Mismatch repair removes and replaces incorrect bases.
487
What enzymes are involved in mismatch repair?
Nuclease DNA polymerase DNA ligase
488
How does the cell distinguish old DNA from new DNA?
Methylases add methyl groups to the original DNA strand.
489
What is transcription?
Copying genetic information from DNA into a complementary RNA sequence.
490
What is translation?
Using RNA information to synthesize proteins.
491
What is mRNA?
Messenger RNA that carries coded information to ribosomes.
492
What is rRNA?
Ribosomal RNA that forms part of ribosomes.
493
What is tRNA?
Transfer RNA involved in protein synthesis.
494
How do bases pair during transcription?
G → C C → G T → A **A → U**
495
Why is uracil used in RNA instead of thymine?
RNA contains uracil instead of thymine, but it base-pairs the same way.
496
If DNA template is 3′-ATGCAT, what is the mRNA sequence?
5′-UACGUA
497
What enzyme is required for transcription?
RNA polymerase.
498
What is the promoter?
The DNA site where RNA polymerase binds to begin transcription.
499
What happens during transcription initiation?
RNA polymerase binds the promoter and unwinds DNA.
500
What happens during transcription elongation?
RNA polymerase moves along DNA, elongating mRNA 5′ → 3′.
501
What happens during transcription termination?
RNA polymerase reaches the terminator and releases the mRNA transcript.
502
What has already been described before translation?
How genetic information in DNA transfers to mRNA during transcription.
503
What is the role of mRNA in protein synthesis?
mRNA serves as the source of information for the synthesis of proteins.
504
What is protein synthesis called?
Translation.
505
Why is protein synthesis called translation?
Because it involves decoding the “language” of nucleic acids and converting it into the “language” of proteins.
506
In what form is the language of mRNA written?
Codons.
507
What is a codon?
A group of three nucleotides, such as AUG, GGC, or AAA.
508
What does the sequence of codons on an mRNA molecule determine?
The sequence of amino acids in the protein being synthesized.
509
What does each codon do?
Each codon codes for a particular amino acid.
510
What is the genetic code?
The relationship between codons and the amino acids they specify.
511
How are the three nucleotides in an mRNA codon designated?
As the first position, second position, and third position of the codon on the mRNA.
512
What does each set of three nucleotides specify?
A particular amino acid.
513
How are amino acids represented in the genetic code?
By a three-letter abbreviation.
514
Which codon specifies methionine?
AUG.
515
What additional role does the codon AUG have?
It is also the start of protein synthesis.
516
What does the word “Stop” identify in the genetic code?
Nonsense codons that signal the termination of protein synthesis.
517
What is translation?
Translation is the process of synthesizing proteins from mRNA.
518
Why is protein synthesis called “translation”?
Because it converts the language of nucleic acids (mRNA) into the language of proteins (amino acids).
519
What is a codon?
A codon is a sequence of three nucleotides on mRNA.
520
What determines the amino acid sequence of a protein?
The sequence of codons on the mRNA.
521
How many possible codons exist?
64 codons.
522
How many amino acids are used in proteins?
20 amino acids.
523
What is meant by “degeneracy of the genetic code”?
Multiple codons can code for the same amino acid.
524
Why is degeneracy of the genetic code beneficial?
It allows some mutations without changing the final protein.
525
What are sense codons?
Codons that code for amino acids (61 codons).
526
What are nonsense (stop) codons?
Codons that signal the end of protein synthesis.
527
What are the three stop codons?
UAA, UAG, UGA.
528
What is the start codon?
AUG.
529
What amino acid does the start codon code for?
Methionine.
530
What amino acid does AUG code for in bacteria?
Formylmethionine (fMet).
531
Why don’t all proteins contain methionine?
The initiating methionine is often removed after translation begins.
532
How are codons read during translation?
Sequentially, one codon at a time.
533
Where does translation occur?
At the ribosome.
534
What is the function of tRNA?
To recognize codons and deliver the correct amino acid to the ribosome.
535
What is an anticodon?
A three-base sequence on tRNA that is complementary to an mRNA codon.
536
How does tRNA ensure the correct amino acid is added?
Each tRNA has a specific anticodon and carries the matching amino acid.
537
What is the main function of the ribosome during translation?
To coordinate codon–anticodon pairing and assemble amino acids into a protein.
538
What is translation?
Translation is the process of using mRNA to synthesize a protein by decoding nucleotide codons into amino acids.
539
Why is protein synthesis called translation?
Because it converts the “language” of nucleic acids (mRNA codons) into the “language” of proteins (amino acids).
540
What is a codon?
A codon is a group of three nucleotides on mRNA that codes for a specific amino acid.
541
What does the genetic code describe?
The relationship between mRNA codons and the amino acids they specify.
542
What is the start codon and what does it code for?
AUG codes for methionine signals the start of translation STARTS IN AUGust
543
What are the three stop (nonsense) codons?
UAA, UAG, UGA
544
What is the difference between sense and nonsense codons?
Sense codons = code for amino acids Nonsense codons = signals end of translation
545
What does “degeneracy” of the genetic code mean?
Multiple codons can code for the same amino acid.
546
What is the advantage of the degeneracy of the genetic code?
It reduces the impact of mutations because some base changes do not alter the amino acid.
547
What is the role of tRNA in translation?
tRNA brings the correct amino acid to the ribosome and matches its anticodon to the mRNA codon.
548
What is an anticodon?
A sequence of three bases on tRNA that is complementary to an mRNA codon.
549
What is the role of the ribosome in translation?
It coordinates codon recognition, tRNA binding, and peptide bond formation to build a protein.
550
What are the three ribosomal sites and their functions?
A ribosome has three spots where tRNA moves during protein synthesis: 1. A site (Amino) - new tRNA carrying an amino acid enters 2. P site (Peptide) - the growing protein chain is held here 3. E site (Exit) - empty tRNA leaves the ribosome TRNA moves through ribosome: A - P - E
551
How does translation begin?
Ribosomal subunits bind mRNA, a tRNA with anticodon UAC pairs with start codon AUG in the P site.
552
What happens during elongation?
Amino acids are added one by one as peptide bonds form and the ribosome moves along the mRNA.
553
When does translation end?
When a stop codon is reached, the ribosome releases the polypeptide and dissociates.
554
In what direction does the ribosome move along mRNA?
5′ → 3′
555
What is a polysome?
Multiple ribosomes translating the same mRNA at the same time.
556
How are transcription and translation related in prokaryotes?
Translation can begin before transcription is complete.
557
Why can translation start before transcription ends in prokaryotes?
Because there is no nucleus and mRNA is produced directly in the cytoplasm.
558
What is the overall goal of translation?
To produce proteins using mRNA as the source of biological information.
559
Where does translation take place in the cell?
At the ribosome.
560
What are the two main roles of the ribosome in translation?
Decodes mRNA information Joins amino acids into a polypeptide chain
561
What role do tRNA molecules play in translation?
They act as “translators” by matching mRNA codons and carrying the correct amino acids.
562
How does a tRNA molecule connect codons to amino acids?
One end recognizes a specific mRNA codon The other end carries the amino acid encoded by that codon
563
How does translation begin?
The ribosome binds to mRNA, and a tRNA pairs with the start codon (AUG) in the P site
564
What happens at the P (peptide) site?
The tRNA holding the growing polypeptide chain is located there
565
What happens at the A (amino) site?
A new tRNA carrying the next amino acid enters and pairs with the mRNA codon A site = tRNA arrives with amino acid
566
When are peptide bonds formed during translation?
When two amino acids are brought together at the ribosome.
567
What happens after a peptide bond forms?
The ribosome moves along the mRNA, shifting the growing peptide to the P site.
568
What occurs at the E (exit) site?
The empty tRNA leaves the ribosome E site = tRNA exits
569
What is elongation in translation?
Repeated cycles of tRNA entry, peptide bond formation, and ribosome movement that lengthen the polypeptide chain.
570
When does translation stop?
When a stop (nonsense) codon on the mRNA is reached.
571
What occurs when translation ends?
Ribosome separates into subunits Polypeptide is released mRNA, tRNAs, and ribosome are reused
572
What is the overall goal of translation?
To produce proteins using mRNA as the source of biological information.
573
Where does translation take place in the cell?
At the ribosome.
574
What are the two main roles of the ribosome in translation?
Decodes mRNA information Joins amino acids into a polypeptide chain
575
What role do tRNA molecules play in translation?
They act as “translators” by matching mRNA codons and carrying the correct amino acids.
576
How does a tRNA molecule connect codons to amino acids?
One end recognizes a specific mRNA codon The other end carries the amino acid encoded by that codon
577
How does translation begin?
The ribosome binds to mRNA, and tRNA pairs with the start codon (AUG) in the P site
578
What happens at the P (peptide) site?
The tRNA holding the growing polypeptide chain is positioned there.
579
What happens at the A (amino) site?
A new tRNA carrying the next amino acid enters and pairs with the mRNA codon.
580
When are peptide bonds formed during translation?
When two amino acids are brought together at the ribosome.
581
What happens after a peptide bond forms?
The ribosome moves along the mRNA, shifting the growing peptide to the P site.
582
What occurs at the E (exit) site?
The empty tRNA leaves the ribosome.
583
What is elongation in translation?
Elongation is the stage of translation where the protein gets longer: 1. Adds a new tRNA with an amino acid 2. Forms a peptide bond 3. Moves along the mRNA This keeps extending the polypeptide chain.
584
When does translation stop?
When a stop (nonsense) codon on the mRNA is reached.
585
What occurs when translation ends?
Ribosome separates into subunits Polypeptide is released mRNA, tRNAs, and ribosome are reused
586
In what direction does the ribosome move along mRNA during translation?
5′ → 3′ direction
587
What happens as a ribosome moves along the mRNA?
The start codon becomes exposed, allowing additional ribosomes to assemble.
588
What happens once the start codon is exposed on an mRNA?
Additional ribosomes can attach and begin synthesizing protein.
589
What is usually observed on a single mRNA molecule during translation?
Multiple ribosomes attached at various stages of protein synthesis.
590
What is a polyribosome?
Many ribosomes translating a single mRNA molecule at the same time.
591
In prokaryotic cells, when can translation begin?
Before transcription is complete
592
Why can translation begin before transcription finishes in prokaryotes?
mRNA is produced in the cytoplasm, so start codons are available to ribosomes before the entire mRNA is made.
593
Which mRNA molecules are transcribed first?
The longest mRNA molecules were transcribed first.
594
What is translation?
The process of decoding mRNA to build a protein.
595
Why is protein synthesis called “translation”?
It converts the nucleic acid “language” into the protein “language.”
596
What is a codon?
A group of 3 mRNA nucleotides that codes for an amino acid.
597
How many possible codons are there?
64 codons
598
How many amino acids are coded for?
20 amino acids
599
What is degeneracy of the genetic code?
Multiple codons can code for the same amino acid.
600
Why is degeneracy important?
It reduces the impact of mutations or misreading.
601
What are sense codons?
Codons that code for amino acids (61 total).
602
What are nonsense (stop) codons?
Codons that end translation (UAA, UAG, UGA) UAA = U ARE AWAY UAG = U ARE GONE UGA = YOU GO AWAY
603
What is the start codon?
AUG
604
What amino acid does AUG code for?
Methionine
605
What is special about the start codon in bacteria?
AUG codes for formylmethionine (fMet).
606
What is the function of tRNA?
Brings amino acids to the ribosome.
607
What is an anticodon?
An anticodon is the 3 base sequence on tRNA that pairs with a codon on mRNA during translation It ensures the correct amino acid is added to the protein A 3 base sequence on tRNA that is complementary to an mRNA codon
608
Where does translation occur?
At the ribosome.
609
What happens at the A site?
Incoming amino acid-tRNA binds.
610
What happens at the P site?
Peptide bond formation; growing chain is held.
611
What happens at the E site?
Empty tRNA exits.
612
What starts translation?
Ribosomal subunits bind mRNA + tRNA (UAC) aligns with AUG.
613
What direction does the ribosome move?
5′ → 3′
614
What happens during elongation?
Amino acids are added one by one via peptide bonds.
615
When does translation stop?
When a stop codon is reached.
616
What happens after termination?
Ribosome subunits separate; protein is released.
617
What is a polyribosome (polysome)?
Multiple ribosomes translating one mRNA at once.
618
Why can translation begin before transcription ends in prokaryotes?
No nucleus; transcription and translation both occur in cytoplasm.
619
Where does transcription occur in eukaryotes?
Nucleus
620
Why must transcription finish before translation in eukaryotes?
mRNA must exit the nucleus and be processed.
621
What are exons?
DNA regions that code for protein.
622
What are introns?
Non-coding DNA regions removed from RNA.
623
What removes introns?
snRNPs (small nuclear ribonucleoproteins).
624
What is RNA splicing?
Removal of introns + joining of exons.
625
What are circRNAs?
Circular RNAs formed from introns (function not fully known).
626
What is gene expression?
Using DNA information to make a functional product.
627
What are the two main steps of gene expression?
Transcription → Translation
628
What directly determines the amino acid sequence of a protein?
The mRNA codon sequence
629
*What does it mean that DNA is complementary?
Each base pairs with a specific partner: A–T and G–C.
630
*Why is complementary base pairing important?
It allows accurate DNA replication and transcription.
631
*What does anti-parallel mean in DNA?
The two strands run in opposite directions (5′→3′ and 3′→5′).
632
*Why is the anti-parallel nature of DNA important?
It allows proper base pairing and is essential for replication and transcription.
633
*What is semi-conservative DNA replication?
Each new DNA molecule contains one original strand and one new strand.
634
*How does anti-parallel DNA relate to semi-conservative replication?
DNA polymerase can only build in the 5′→3′ direction, so each strand is copied differently.
635
*What is a gene?
A segment of DNA that contains the information needed to produce a functional product (usually a protein).
636
*How is a gene expressed?
Through transcription and translation.
637
*Where is DNA located in prokaryotes?
In the cytoplasm (no nucleus).
638
*Where is DNA located in eukaryotes?
Inside the nucleus.
639
*What major structural feature is common in eukaryotic genes but not prokaryotic genes?
Introns and exons.
640
*Where does DNA replication occur in bacteria?
In the cytoplasm.
641
*Why is DNA replication in bacteria fast?
Bacteria have a single circular chromosome and no nucleus.
642
*What is transcription?
The process of copying DNA into mRNA.
643
*What enzyme is required for transcription?
RNA polymerase.
644
*What happens during initiation?
RNA polymerase binds to the promoter.
645
*What happens during elongation?
RNA polymerase builds mRNA in the 5′→3′ direction.
646
*What happens during termination?
RNA polymerase reaches the terminator and releases mRNA.
647
*What are exons?
DNA regions that code for protein.
648
*What are introns?
Non-coding DNA regions removed from RNA.
649
*What removes introns in eukaryotic cells?
snRNPs (small nuclear ribonucleoproteins).
650
*What is RNA splicing?
Removal of introns and joining of exons.
651
*What is the role of mRNA?
It carries genetic information from DNA to the ribosome.
652
*Why is mRNA important in vaccines?
It provides instructions to make a specific protein.
653
**What is the genetic code?
The relationship between mRNA codons and amino acids.
654
**What is a codon?
A sequence of 3 mRNA nucleotides.
655
**What does AUG code for?
Methionine (start codon).
656
**What molecules are required for translation?
mRNA, tRNA, ribosomes, amino acids.
657
**What is the function of tRNA?
Delivers amino acids to the ribosome.
658
**What is an anticodon?
A 3-base sequence on tRNA complementary to an mRNA codon.
659
**Where does translation occur?
At the ribosome.
660
**What happens during initiation?
Initiation = start - ribosome starts at AUG Elongation = amino acid added Termination = stop codon ends translation Initiation = ribosomal subunits binds to mRNA and the start codon is positioned to begin translation
661
*What happens during elongation?
Amino acids are added via peptide bonds.
662
*What happens during termination?
A stop codon is reached and the protein is released.
663
*Why can translation begin before transcription ends in prokaryotes?
There is no nucleus.
664
*Why can’t this happen in eukaryotes?
Transcription occurs in the nucleus and mRNA must be processed first.
665
*What is the final product of translation?
A polypeptide (protein).
666
*What is the “central dogma” of molecular biology?
The typical flow of genetic information in a cell: DNA → mRNA → Protein → Function.
667
*In the central dogma, what is the role of DNA?
DNA stores the genetic information that serves as the template for making mRNA.
668
*What molecule is produced directly from DNA?
mRNA (messenger RNA).
669
*What is the role of mRNA in the central dogma?
mRNA carries the genetic instructions from DNA to be used to make a protein.
670
*What is produced from mRNA?
A protein.
671
*Why are proteins important in the central dogma?
Proteins determine cellular function.
672
*What is the final outcome of the central dogma pathway?
Function (normal cellular activity).
673
*How does a mutation alter the central dogma pathway?
A mutation changes the DNA, which can affect every downstream step.
674
*What happens first when DNA is mutated?
Mutated DNA is produced.
675
*What does mutated DNA produce during transcription?
Mutated mRNA.
676
*What is the result of mutated mRNA during translation?
An altered protein.
677
*How can an altered protein affect the cell?
It can lead to altered function.
678
*Does every mutation always change function?
Not necessarily — but mutations can lead to altered protein structure and function.
679
*Summarize how mutations affect phenotype using the central dogma.
Mutated DNA → mutated mRNA → altered protein → altered function.
680
*What causes many bacterial diseases?
The presence of toxic proteins that damage human tissue.
681
*Where are toxic bacterial proteins encoded?
They are coded for by bacterial genes.
682
*How do bacterial genes contribute to disease?
Bacterial genes encode toxic proteins that harm host tissues.
683
*What type of toxin does Vibrio cholerae produce?
An enterotoxin.
684
*What is an enterotoxin?
A toxin that affects the intestinal tract.
685
*What symptoms are caused by the enterotoxin produced by Vibrio cholerae?
Diarrhea and severe dehydration.
686
*Why is infection with Vibrio cholerae potentially fatal?
Severe dehydration caused by diarrhea can be fatal if left untreated.
687
*What is one of the first steps toward the development of antibiotic resistance?
Mutations in the bacterial genome.
688
*How do genetic mutations contribute to antibiotic resistance?
Mutations can allow bacteria to survive exposure to antibiotics, leading to resistant populations.
689
*Which bacterium is highlighted as an example of antibiotic resistance in this slide?
Staphylococcus aureus.
690
*To which class of antibiotics is Staphylococcus aureus now resistant in this example?
Beta-lactam antibiotics, such as penicillin.
691
*Why was methicillin introduced?
To treat penicillin-resistant Staphylococcus aureus.
692
*What does MRSA stand for?
Methicillin-resistant Staphylococcus aureus.
693
*What has happened to methicillin-resistant Staphylococcus aureus (MRSA) over time?
It has become a leading cause of healthcare-associated infections.
694
*What does this slide demonstrate about antibiotic use and bacterial evolution?
Antibiotic use can select for mutant bacteria, leading to resistance.
695
*How does this slide connect genetics to public health?
Genetic mutations in bacteria can result in antibiotic-resistant infections that are difficult to treat.
696
*What is biotechnology in the context of genetics?
The ability of scientists to alter a microorganism’s genome by adding genes that produce useful human proteins.
697
*How can scientists alter a microorganism’s genome?
By adding genes that encode specific proteins.
698
*What type of proteins can microorganisms be engineered to produce?
Human proteins used in treating disease.
699
*What human protein is given as an example of biotechnology in this slide?
Insulin.
700
*What disease is insulin used to treat?
Diabetes.
701
*How is insulin produced according to this slide?
By genetically modifying microorganisms to produce human insulin.
702
*How does DNA expression affect a cell?
DNA expression leads to cell function via the production of proteins.
703
*What directly links DNA to cell function?
Protein production.
704
*How can DNA expression be regulated in bacteria?
By operons.
705
*What do mutations do to DNA?
Mutations alter DNA sequences.
706
*How can DNA mutations affect bacteria?
DNA mutations can change bacterial function.
707
*What is the overall connection between DNA, mutation, and function highlighted in this slide?
Changes in DNA (through expression control or mutation) can alter protein production and bacterial function.
708
*What are biofilms?
Communities of bacteria that attach to surfaces and grow together in a structured layer.
709
*What causes biofilm formation at the genetic level?
Altered bacterial gene expression.
710
*When do bacteria begin producing biofilms?
When bacterial populations become large enough.
711
*What everyday object is shown as an example of a surface where biofilms grow?
A toothbrush bristle.
712
*Which genus of bacteria is associated with biofilm formation on teeth and gums?
Streptococcus.
713
Which specific Streptococcus species is *named in this slide?
Streptococcus mutans (S. mutans).
714
*Where do Streptococcus species form biofilms in the human body?
On teeth and gums.
715
*What dental condition is associated with biofilm formation on teeth?
Dental plaque.
716
*What disease can result from dental plaque caused by biofilms?
Dental caries (cavities).
717
*What is the overall significance of biofilms in this slide?
Biofilms show how changes in gene expression can alter bacterial behavior and cause disease.
718
*Why are biofilms clinically important?
They contribute to disease development and are harder to remove or treat.
719
*Define Genetics
The study of what genes are, how they carry information, how information is expressed, and how genes are replicated
720
*Define Gene
A segment of DNA that encodes a functional product, usually a protein
721
*Define Genome
The entire genetic complement of an organism, includes its genes and nucleotide sequences
722
*What is the central dogma of molecular biology?
The flow of genetic information from DNA → RNA → Protein.
723
*What is complementary base pairing?
A specific pairing of nitrogenous bases based on hydrogen bonding.
724
*Which bases pair together in DNA?
Adenine (A) pairs with Thymine (T) and Guanine (G) pairs with Cytosine (C).
725
*Which bases pair together in RNA?
Adenine (A) pairs with Uracil (U) and Guanine (G) pairs with Cytosine (C).
726
*Which base pair occurs in both DNA and RNA?
Guanine–Cytosine (G–C).
727
*Which base pair is unique to DNA?
Adenine–Thymine (A–T).
728
*Which base pair is unique to RNA?
Adenine–Uracil (A–U).
729
*What type of bond holds complementary base pairs together?
Hydrogen bonds.
730
*How many hydrogen bonds form between Guanine and Cytosine?
Three hydrogen bonds.
731
*How many hydrogen bonds form between Adenine and Thymine?
Two hydrogen bonds.
732
*How many hydrogen bonds form between Adenine and Uracil?
Two hydrogen bonds.
733
*Why is complementary base pairing important?
It ensures accurate DNA replication and transcription.
734
*Why can Guanine not pair with Adenine?
Their hydrogen bonding patterns do not match.
735
*What determines which bases can pair together?
The number and position of hydrogen bond donors and acceptors️.
736
*What base replaces thymine in RNA?
Uracil (U).
737
*What type of process is DNA replication?
An anabolic polymerization process.
738
*What monomers are required for DNA replication?
Nucleotides.
739
*What form of energy is required for DNA replication?
ATP.
740
*What structural feature of DNA is key to replication?
The complementary structure of the two strands.
741
*What does complementary structure mean in the context of replication?
Each base on one strand determines the correct base added to the new strand.
742
*What does “semiconservative replication” mean?
Each new DNA molecule contains one original (parental) strand and one new (daughter) strand.
743
*How many original strands are present in each replicated DNA molecule?
One original strand.
744
*How many newly synthesized strands are present in each replicated DNA molecule?
One daughter strand.
745
*Why is semiconservative replication important?
It ensures accurate copying of genetic information.
746
*What is the purpose of DNA replication?
To copy DNA so each daughter cell receives a complete genome.
747
*Where does DNA replication begin on the DNA molecule?
At a replication fork.
748
*What happens first during DNA replication?
Enzymes unwind the parental double helix.
749
*What is the parental strand?
The original DNA strand used as a template for replication.
750
*Why must the unwound DNA be stabilized?
To prevent the strands from re-annealing.
751
*What proteins stabilize the unwound parental DNA?
Single-strand binding proteins (often just called stabilizing proteins).
752
*In what direction does DNA polymerase synthesize new DNA?
5′ → 3′
753
Why can DNA polymerase only work in the 5′ → 3′ direction?
Because nucleotides can only be added to the 3′ end.
754
*What is the leading strand?
The strand synthesized continuously toward the replication fork.
755
*Which enzyme synthesizes the leading strand?
DNA polymerase.
756
*What is the lagging strand?
The strand synthesized discontinuously away from the replication fork.
757
*Why is the lagging strand synthesized discontinuously?
Because DNA polymerase can only synthesize DNA 5′ → 3′, opposite fork movement.
758
*Why is an RNA primer needed for DNA replication?
DNA polymerase cannot start synthesis on its own.
759
*Which enzyme synthesizes the RNA primer?
RNA polymerase (primase).
760
*What are Okazaki fragments?
Short DNA fragments synthesized on the lagging strand.
761
Which strand contains Okazaki fragments?
The lagging strand.
762
What happens to the RNA primers after DNA synthesis?
They are digested and replaced with DNA.
763
Which enzyme replaces RNA primers with DNA?
DNA polymerase.
764
What enzyme joins Okazaki fragments together?
DNA ligase.
765
What is the role of DNA ligase?
To seal gaps between DNA fragments on the lagging strand.
766
Which strand is synthesized continuously?
Leading strand.
767
Which strand requires multiple RNA primers?
Lagging strand.
768
What enzyme is responsible for most DNA synthesis?
DNA polymerase.
769
Which enzyme is NOT used on the leading strand after initiation?
DNA ligase (mainly needed for lagging strand).
770
*Function of DNA Helicase
unwinded double stranded DNA
771
*Function of DNA Gyrase
relaxes supercoiling ahead of the replication fork
772
*Function of DNA Polymerase
Synthesize DNA; Proofread and faciliate repair of DNA
773
*Function of RNA Polymerase
Synthesize short RNA primers on the lagging strand
774
*Function of DNA Ligase
Joins Okazaki fragments together on lagging strand
775
*Where does DNA polymerase add new nucleotides during DNA replication?
To the hydroxyl (–OH) group at the 3′ end of the nucleic acid.
776
*Why can DNA polymerase only add nucleotides to the 3′ end?
Because DNA polymerase requires a free 3′ hydroxyl group to form a phosphodiester bond.
777
*Why are the two new DNA strands synthesized differently during replication?
Because the two parental DNA strands are anti-parallel.
778
*How is the leading strand synthesized?
Continuously.
779
*Why is the leading strand synthesized continuously?
Because it is synthesized in the same direction as the replication fork opens.
780
*How is the lagging strand synthesized?
Discontinuously.
781
*Why is the lagging strand synthesized discontinuously?
Because DNA polymerase can only synthesize DNA 5′ → 3′, which is opposite the direction of fork movement on this strand.
782
*Which strand is continuous: leading or lagging?
Leading strand
783
*Which strand is discontinuous: leading or lagging?
Lagging strand
784
*Define Transcription
information in DNA is copies as RNA nucleotides sequences
785
*What are the three types of RNA transcribed from DNA?
Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA)
786
*What is the role of messenger RNA (mRNA)?
It carries genetic information from DNA to the ribosome for protein synthesis.
787
*What is the role of ribosomal RNA (rRNA)?
It forms the structural and functional core of the ribosome.
788
*What is the role of transfer RNA (tRNA)?
It transfers amino acids to the ribosome during translation.
789
*Where does transcription occur in prokaryotic cells?
In the nucleoid.
790
* What are the steps in the process of transcription?
Initiation – RNA polymerase binds to the promoter, and the DNA unwinds at the start of the gene. Elongation – RNA polymerase moves along the template strand of DNA, adding complementary RNA nucleotides (A–U, C–G) to synthesize RNA. Termination – RNA polymerase reaches the terminator, releases the RNA transcript, and the DNA rewinds into a double helix.
791
What enzyme carries out transcription?
RNA polymerase
792
Where does transcription begin on the DNA?
At the promoter (the beginning of a gene).
793
What happens when RNA polymerase binds to the promoter?
RNA polymerase binds to DNA DNA unwinds at the start of the gene
794
Which DNA strand is used as the template during transcription?
The template strand of DNA
795
How is RNA synthesized during transcription?
By complementary base pairing of free RNA nucleotides with DNA bases on the template strand.
796
How does RNA base pairing differ from DNA base pairing?
DNA: A–T RNA: A–U (uracil replaces thymine)
797
In what direction does RNA polymerase move along DNA?
RNA polymerase moves along the DNA as RNA is synthesized.
798
What happens to DNA behind RNA polymerase as transcription proceeds?
The DNA rewinds after it has been transcribed.
799
What signals the end of transcription?
The terminator (end of the gene).
800
What happens when transcription reaches the terminator?
RNA polymerase stops transcription RNA polymerase is released The complete RNA strand is released DNA helix re-forms
801
Put the steps of transcription in order:
RNA polymerase binds promoter DNA unwinds RNA synthesized by complementary base pairing RNA polymerase moves along DNA DNA rewinds behind enzyme Terminator reached RNA and RNA polymerase released
802
What is the final product of transcription?
A complete RNA strand (usually mRNA)
803
How does transcription and RNA processing occur in eukaryotes?
1. Transcription - in nucleus - RNA polymerase transcribes DNA - The gene contains exons and introns 2. RNA Processing (splicing) - introns are removed - exons are joined together - this forms mature mRNA 3. Export to cytoplasm - mature mRNA leaves the nucleus - it enters the cytoplasm for translation (protein synthesis)
804
*Where does RNA Transcription occur?
in the nucleus
805
*RNA is translated to form ____
polypeptides
806
translation
Translation is the process where mRNA is used to build a polypeptide (protein).
807
Steps of Translation
1. Initiation: - Start the protein - mRNA attaches to a ribosome - ribosome finds the start codon (AUG) - tRNA with complementary anticodons binds, bringing the first animo acid (methionine) 2. Elongation (BUILD) - ribosome moves along the mRNA one codon at a time - tRNA brings amino acids - Peptide bonds form, linking amino acids - The polypeptide chain grows - **builds the protein** 3. Termination (STOP) - ribosome reaches a stop codon ends translation - Translation stops - the completed protein is released - **release the protein**
808
How is mRNA read during translation?
In codons (groups of three nucleotides).
809
What does each codon specify?
One amino acid.
810
Where does translation begin on the mRNA?
At the start codon.
811
What is the start codon?
AUG.
812
What amino acid does AUG code for?
Methionine.
813
Where does translation end?
At a stop codon.
814
What are the three stop codons?
UAA, UAG, UGA.
815
What happens when a stop codon is reached?
Translation stops and the polypeptide is released.
816
What is the genetic code?
A set of rules that determines how a nucleotide sequence is converted into an amino acid sequence.
817
What does the genetic code translate?
mRNA codons into amino acids.
818
What is a codon?
A sequence of three nucleotides on mRNA.
819
What does each codon represent?
One specific amino acid or a stop signal.
820
How many amino acids are encoded by the genetic code?
20 universal amino acids.
821
Can more than one codon code for the same amino acid?
Yes.
822
What is this property of the genetic code called?
Degeneracy (or redundancy).
823
Which amino acid is a common example of having multiple codons?
Leucine (Leu).
824
How is the codon chart read?
1️⃣ First nucleotide (5′ position) 2️⃣ Second nucleotide 3️⃣ Third nucleotide (3′ position)
825
What codon signals the start of translation?
AUG.
826
What amino acid does the start codon code for?
Methionine.
827
What are the three stop codons?
UAA, UAG, UGA.
828
What do stop codons code for?
No amino acid — they signal the end of translation.
829
Process of Translation
1. Initiation - mRNA binds to a ribosome - Ribosome finds the start codon (AUG) - tRNA carrying the first amino acid binds in the P site 2. Elongation - a new tRNA enters the A site - the amino acids form a peptide bond - the ribosome moves along the mRNA - the growing polypeptide chain lengthens 3. Termination - ribosome reaches a stop codon ends translation - polypeptide is released - ribosome separates
830
What is the central principle (central dogma) of genetics?
Genetic information flows from DNA → RNA → Protein.
831
What does DNA represent in the central principle?
The genotype (genetic information).
832
What process converts DNA into RNA?
Transcription.
833
What type of RNA is produced during transcription?
mRNA (messenger RNA).
834
In what direction is mRNA synthesized?
5′ → 3′.
835
What process converts mRNA into a polypeptide?
Translation.
836
Where does translation occur?
At the ribosome.
837
What is produced during translation?
A polypeptide (protein).
838
What do the circles labeled Methionine, Arginine, Tyrosine, and Leucine represent?
Amino acids.
839
What determines the order of amino acids in a polypeptide?
The sequence of codons in mRNA.
840
What does the NH₂ label indicate on the polypeptide?
The N-terminus (start) of the protein.
841
What is a phenotype?
The observable traits produced by protein function.
842
How does genotype relate to phenotype?
DNA (genotype) → RNA → protein, which determines phenotype.
843
Why is methionine shown first in the polypeptide?
It is coded by the start codon (AUG). Ended by Leucine
844
What would happen if the DNA sequence changed?
The mRNA and amino acid sequence could change, altering the protein and phenotype.
Microbiology
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