1
Q
What is the basic unit of DNA structure?
A
The nucleotide
A nucleotide consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base.
2
Q
List the nitrogenous bases found in DNA.
A
- Adenine (A)
- Guanine (G)
- Thymine (T)
- Cytosine (C)
These bases pair specifically: A with T, and G with C.
3
Q
What bonds the nitrogenous bases to the sugar in DNA?
A
Covalent bonds
Nitrogenous bases bond to the 1’ carbon of the sugar.
4
Q
How do adenine and thymine pair in DNA?
A
With 2 hydrogen bonds
This is part of the complementary base pairing.
5
Q
How do guanine and cytosine pair in DNA?
A
With 3 hydrogen bonds
This stronger pairing contributes to the stability of DNA.
6
Q
What is the orientation of the two strands of DNA?
A
Antiparallel
One strand runs 5’ to 3’ while the other runs 3’ to 5’.
7
Q
What is the process called that covalently bonds nucleotide subunits into polymers?
A
Dehydration synthesis
This process forms the sugar-phosphate backbone of DNA.
8
Q
Define genetics.
A
The study of heredity
It involves transmission of biological traits from parent to offspring.
9
Q
Who demonstrated that DNA was the genetic material in 1928?
A
Frederick Griffith
He showed that bacteria can transfer genetic information through a biochemical agent.
10
Q
What did Erwin Chargaff discover about DNA?
A
The ratios of nucleotides: G=C, A=T
His findings supported the base pairing rules in DNA.
11
Q
What did Hershey and Chase prove in 1950?
A
Genetic information is made from DNA, not protein
They used radiolabeled molecules to track which entered bacteria.
12
Q
What technique did Rosalind Franklin use to discover DNA’s shape?
A
X-ray diffraction
Her work provided critical data for understanding DNA’s structure.
13
Q
What is the semi-conservative nature of DNA replication?
A
Each new DNA molecule contains one old strand and one new strand
This ensures accurate copying of genetic information.
14
Q
What enzyme unwinds and unzips the DNA double helix during replication?
A
Helicase
It creates the replication fork for synthesis.
15
Q
What is the function of primase in DNA replication?
A
Synthesizes an RNA primer
This primer initiates the synthesis of new DNA strands.
16
Q
What are Okazaki fragments?
A
Short segments synthesized on the lagging strand
They are formed because DNA is synthesized discontinuously.
17
Q
What is the role of DNA polymerase I?
A
Replaces RNA primers with DNA
It also repairs mismatched bases.
18
Q
What is the sum of genetic material in a cell called?
A
Genome
It includes all DNA present in an organism.
19
Q
What distinguishes prokaryotic genomes from eukaryotic genomes?
A
Prokaryotic genomes are circular, while eukaryotic genomes are linear
Eukaryotic genomes are located in the nucleus.
20
Q
What is the central dogma of biology?
A
Replication, Transcription, Translation
It describes the flow of genetic information.
21
Q
What is the difference between genotype and phenotype?
A
Genotype is all genes present, phenotype is the observable traits
Genotype determines potential characteristics, while phenotype is the expressed result.
22
Q
What is an organism?
A
The nucleic acid instructions for an organism’s potential characteristics
Nucleic acids include DNA and RNA, which carry genetic information.
23
Q
Define phenotype.
A
The result of gene expression & protein synthesis - the observable traits of an organism
Phenotype is influenced by both genetic and environmental factors.
24
Q
What is a chromosome?
A
Subdivided into genes, the fundamental unit of heredity responsible for a given trait
Chromosomes are structures within cells that contain DNA.
25
List the three basic categories of genes.
* Genes that code for proteins – structural genes
* Genes that code for RNA
* Genes that control gene expression – regulatory genes
## Footnote
Each category plays a distinct role in the genetic makeup and function of an organism.
26
How many genes does the smallest virus contain?
4 to 5 genes
## Footnote
This small number reflects the simplicity of viral genomes.
27
How many genes are present in a single E. coli chromosome?
4,288 genes
## Footnote
E. coli serves as a model organism in microbiology and genetics.
28
How many chromosomes and genes are found in a human cell?
46 chromosomes containing 31,000 genes
## Footnote
Humans have a complex genome that contributes to diverse traits.
29
What allows the genome to fit inside a cell?
Sophisticated packaging
## Footnote
This includes compacting the DNA molecule through various means.
30
What are supercoils?
The compacting method of DNA in the cell
## Footnote
Supercoiling helps to efficiently organize DNA within the limited space of the cell.
31
In prokaryotes, how is DNA compacted?
By the action of the enzyme DNA gyrase
## Footnote
DNA gyrase introduces reversible twists into the DNA molecule.
32
How is DNA packaging in eukaryotes different from prokaryotes?
More complex, with three or more levels of coiling, starting with nucleosomes
## Footnote
Nucleosomes consist of DNA wrapped around histone proteins, forming the basic unit of DNA packaging.
33
What is mRNA splicing?
Introns are cut out and exons are 'glued' together
34
What is the purpose of mRNA capping?
'Cap' acts as a protective destination label
35
What does the 'poly A tail' do?
Resists endonuclease digestion
36
What is the function of mRNA?
Carries the DNA master code to the ribosomes
37
What does tRNA carry?
Carries amino acids to ribosomes during translation
38
What is the role of ribosomal RNA (rRNA)?
Forms the major part of ribosomes and participates in protein synthesis
39
What is the function of primer RNA?
Primes DNA for replication
40
What is the significance of codons?
Message is in triplets called codons
41
What is the structure of tRNA?
75 to 95 nucleotides in length, bent into hairpin loops forming a cloverleaf structure
42
What do the bottom loop of tRNA exposes?
The tRNA specific anticodon complementary to an mRNA codon
43
What are the two subunits of ribosomes?
One large subunit and one small subunit
44
What is the difference between prokaryotic and eukaryotic ribosomes?
70s for prokaryotic and 80s for eukaryotic
45
What is the gene-protein connection?
Each structural gene codes for a protein's primary structure
46
What is the genetic code?
Universal, with a triplet of bases (codon) specifying one amino acid
47
What are the stop codons?
UAA, UGA, UAG
48
What marks the beginning of translation?
An initiation codon
49
What marks the end of translation?
A stop codon
50
What are the three stages of translation?
* Initiation * Elongation * Termination
51
What is the first step in translation initiation?
Ribosome attaches to the 5’ end of an mRNA
52
What happens during translation elongation?
2nd tRNA brings an amino acid to the ribosome, peptide bond forms
53
What happens during translation termination?
Ribosome reaches a stop codon, polypeptide is released
54
What is the primary structure of proteins?
Amino acid sequence
55
What is the secondary structure of proteins?
Pleating/helical structure formed from inter-molecular bonds
56
What is the tertiary structure of proteins?
3-D protein folding in upon itself
57
What is the quaternary structure of proteins?
Two or more polypeptides interfolded together
58
What are prion diseases?
Misfolded prion proteins disrupt functions of normally folded ones
59
What is the role of genes in gene expression?
Genes are 'switched on' or 'off' as needed
60
What is an operon?
A set of genes regulated as a single unit in prokaryotes
61
What are the two types of operons?
* Inducible * Repressible
62
What is the lac operon?
An inducible operon made of three segments
63
What does the regulator gene in the lac operon do?
Codes for a repressor
64
What is the function of β-galactosidase?
Hydrolyzes lactose
65
What does the permease do?
Brings lactose across cell membrane
66
What is the function of the lacA gene?
Codes for transacetylase
67
What is the significance of constitutive genes?
They are always expressed and do not require regulation
68
What does the lacY gene code for?
Permease, which transports lactose across membranes.
69
What does the lacZ gene code for?
β-galactosidase, which hydrolyzes lactose into glucose and galactose.
70
What is an operon?
A group of genes that are regulated together.
71
What is a repressible operon?
An operon that is normally on and can be turned off when its product is no longer required.
72
What role does arginine play in the operon regulation?
Arginine acts as a corepressor that binds to the repressor and blocks arginine synthesis.
73
What is a mutation?
A change in phenotype due to a change in genotype (nitrogen base sequence of DNA).
74
What is a wild type?
A natural, nonmutated characteristic of an organism.
75
What is a mutant strain?
An organism that has undergone a mutation and shows variance in characteristics.
76
What are spontaneous mutations?
Random changes in DNA due to errors in replication that occur without known cause.
77
What are induced mutations?
Mutations that result from exposure to known mutagens.
78
What are mutagens?
Agents that increase mutation rates above spontaneous rates.
79
Name some chemical mutagens.
* Smoke (benzopyrenes)
* Alcohol
* Gasoline
* Benzene
* Aflatoxin
* 5-bromouracil
80
What are physical mutagens?
* Non-ionizing radiation (e.g., UV)
* Ionizing radiation (e.g., X-rays, Gamma rays)
81
What are biological mutagens?
Oncoviruses, e.g., HPV and Hepatitis B.
82
What is a missense mutation?
A mutation that causes a single amino acid change in the peptide.
83
What is a nonsense mutation?
A mutation that changes a normal codon into a STOP codon.
84
What is a silent mutation?
A mutation that has little effect on the product, often resulting in the same amino acid.
85
What is a frameshift mutation?
A mutation caused by insertions or deletions that changes the reading frame of codons.
86
What is the role of DNA polymerase III in DNA repair?
Checks replication errors during replication.
87
What is mismatch repair?
A proofreading process carried out by DNA polymerase I on the replicated strand.
88
What is excision repair?
A process where damaged nucleotides and sections of DNA are removed and replaced.
89
What is photoactivation repair?
A DNA repair mechanism that requires photolyases and light, found only in bacteria.
90
What is xeroderma pigmentosum?
A genetic disease caused by UV-induced mutations in DNA due to faulty repair systems.
91
What is the Ames test?
A test that uses mutant Salmonella bacteria to assess the mutagenicity of chemicals.
92
What is genetic recombination?
The acquisition and expression of genes that originated in another organism.
93
Name the three means of genetic recombination in bacteria.
* Conjugation
* Transformation
* Transduction
94
What are plasmids?
Extrachromosomal circular DNA that carry non-essential genes, providing a selective advantage.
95
What is conjugation in bacteria?
The transfer of a plasmid or chromosomal fragment from a donor cell to a recipient cell via direct contact.
96
What occurs during Hfr transfer?
A portion of the donor's chromosome and the fertility plasmid are transferred to the recipient.
97
What is the promoter region?
The sequence that signals where transcription of a gene begins.
98
What does Hfr stand for?
High frequency of recombination
## Footnote
Hfr cells are capable of transferring chromosomal genes during conjugation.
99
What is the process of Hfr transfer?
Transmission of chromosomal genes from a donor cell to a recipient cell
## Footnote
The donor chromosome is duplicated and integrated into the recipient's chromosome.
100
What is transformation in bacteria?
Acceptance of chromosomal fragments from a lysed cell by a recipient cell
## Footnote
Transformation can occur between unrelated donor and recipient cells.
101
What role does a bacteriophage play in transduction?
Carrier of DNA from a donor cell to a recipient cell
## Footnote
Transduction can be generalized or specialized.
102
What are the two types of transduction?
* Generalized transduction
* Specialized transduction
103
What is the main difference between generalized and specialized transduction?
Generalized transduction involves random DNA fragments; specialized transduction involves specific parts of the host genome
## Footnote
In generalized transduction, any gene can be transmitted.
104
What factors are involved in direct genetic recombination?
Donor cell with pilus and fertility plasmid
## Footnote
Both donor and recipient cells must be alive for direct transfer.
105
What is an example of indirect genetic recombination?
Transformation
## Footnote
In transformation, the donor is usually dead and the recipient is a live competent cell.
106
What types of genes can be transferred through conjugation?
* Drug resistance
* Resistance to metals
* Toxin production
* Enzymes
* Adherence molecules
* Degradation of toxic substance
* Uptake of iron
107
What are the positive effects of mutations?
Beneficial mutations can lead to adaptation, survival, and reproduction
## Footnote
These mutations can confer advantages during selection pressures.
108
What are the negative effects of mutations?
Lead to nonfunctional proteins, which can be harmful or fatal
## Footnote
Harmful mutations can negatively impact an organism's fitness.
109
What is the role of RNA polymerase during transcription initiation?
Binds to the promoter and unzips the DNA
## Footnote
This process is essential for starting the transcription of a gene.
110
In which direction is RNA synthesized during transcription?
5’ to 3’ direction
## Footnote
The DNA template strand is read in the 3’ to 5’ direction.
111
What happens when RNA polymerase reaches the termination site?
It releases the RNA transcript
## Footnote
The length of the RNA transcript can vary from 100 to 1,200 bases.
112
Fill in the blank: During transcription, RNA polymerase synthesizes RNA using only _______.
One strand of DNA
113
What is a competent recipient cell?
A live cell capable of taking up free DNA
## Footnote
Competent cells can incorporate DNA fragments through transformation.
114
What is the significance of binary fission in microbes?
Allows rapid multiplication and the potential for significant mutation accumulation
## Footnote
Microbes can produce millions of offspring in a short time, leading to quick spread of beneficial mutations.
115
True or False: Only beneficial mutations are retained in a population.
False
## Footnote
Harmful mutations can lead to nonfunctional proteins and may be eliminated from the population.
116
Although most genome exists as chromosomes , they can also be..
Bacteria and fungi are plasmids (tiny extra pieces of DNA)
Mitochondria and chloroplasts of euk.have their own functional chromosomes
117
How is the structure in chromosomes different in in euk. and bacterial cells?
Euk. chromosomes consist of a DNA molecule w/ histome proteins
Bacterial chromosome is condensed and secured into a packet by a dif type of protein
118
Where are eukaryotic chromosomes located
Nucleus
119
Types of eukaryotic chromosome
Diploid (pair)
Haploid (single)
Linear in format
120
Types of chromosomes bacteria have
Single single circular chromosome
Multiple chromosomes
Few linear chromosomes
121
122
What is a gene
Specific segment of DNA that contains the necessary codes to make a molecule of protein or RNA
123
3 categories of genes
Structural genes (code for proteins)
Genes that code for RNA
Regulatory genes (control gene expression)
124
The collection of the types of genes constitutes an organisms …
Genotype
125
126
127
How is DNA packed into a cell
Supercoils or superhelices
128
In prok. how is the circular chromosome packed with dna
Enzyme called topoisomerase (DNA gyrase)
129
What does DNA gyrase (topoisomerase) do in prok.
Coils the chromosome into a tight bundle by introducing a reversible series of twists into the DNA molecule W
130
Is the packaging of dna in eukaryotes more complex?
Yes it has three or more levels of coiling
131
How is a eukaryote packaged with dna
The DNA molecule of a chromosome is wound twice around the histone proteins creating a chain of nucleosomes
Nucleosomes spiral upon one another, creates a greater supercoilimg when it twists on its radius into a giant spiral w loops from outside
This is what makes it visible for mitosis
132
Coiling of DNA also serves to make segments of of the genetic program
___ avaliable
Either more or less
To control when genes are accessed
133
Basic unit of DNA structure is
Nucleotides
Composed of phosphate, deoxyribose sugar, and a nitrogen base
134
What is on the 5’ and 3’ prime on DNA
5’ is carbon on deoxyribose
3’ is carbon
135
Where do the nitrogen bases purine and pyrimidines attach
Attach by covalent bonds at the 1’ position of the sugar
136
When the nitrogen bases (purine and pyrimidine) span the center of the molecule and bind w their complimentary bases from the opposite strand, the form..?
A double helix
137
What are the paired bases (purine and pyrimidine paired up w their match) held by
Hydrogen bonds which can be disrupted, allowing the molecule to be unzipped into 2 strands
138
How many hydrogen bonds does adenine and thymine make together
2
139
How many hydrogen bonds does cytosine and guanine make
3
140
How does the cell replicate in a bacteria cell
Binary fission or budding
Also involves accurate duplication and seperatiom of the genetic material into each daughter cell to ensure they have functional genome
141
Simplified version of replication (3 steps) dna
1. Uncoiling the parent DNA molecule, beginning at a predetermined point of origin
2. unzipping the hydrogen bonds between the base pairs, separating the 2 strands and exposing the nucleotide sequence of each strand to serve as templates
3. Synthesizing 2 new strands by using the single stranded template as a pattern for adding the correct complimentary nucleotides to the newly forming strand
142
Helical
Unzipping the dna helix
143
Primase
Synthesizing an RNA primer
144
DNA polymerase III
Adding bases to the new DNA chain; proofreading the chain for mistakes
145
DNA polymerase I
Removing RNA primers, replacing gaps btwn Okazaki fragments w correct nucleotides, repairing mismatched bases
146
Ligase
Final binding of nicks in DNA during synthesis and repair
147
Gyrase
Supercoiling
148
All chromosomes have a specific origin of
Replication
149
Since the strands are rich with A-T , do they need a lot of energy to split the two strands
Less energy is required to separate the two strands than would be required if the origin were rich in guanine and cytosine
150
Process of synthesizing a new daughter strand of DNA using the parental strand as a template is carried out by a giant enzyme complex that brings in primary replication enzyme..l
DNA Polymerase III
151
Can DNA polymerase add nucleotides to a DNA template strand?
Can’t add without a guide that can serve as the starting point for nucleotides to be bonded during synthesis
152
Before replication, what is added at the origin of replication
Piece of RNA called a primer to provide the first nucleotide with a free 3’ OH group for binding
153
In what direction can DNA polymerase read the template
3’ to 5’
154
In what direction can DNA polymerase add nucleotides
Add to the newly synthesized strand only in 5’ to 3’ direction
155
What does helicase untwist? Step 1
The helix and break the hydrogen bonds holding two strand tg, resulting in two separate strands
156
Replication begins when RNA ___ are synthesized by primase at the origin of replication Step 1
Primers
157
DNA polymerase III will use this short strand of __ as a starting point for adding ____ step 1
RNA
nucleotides
158
How many replication forks are there in the circular DNA molecule of bacteria step 1
Two
Each containing its own set of replication enzymes
159
What does each replication forks require step 1
2 active DNA polymerases along w several other proteins and enzymes whose main functions are to stabilize the polymerase and provide a means of removing and replacing nucleotides
160
What does the enzyme complex encircle Step 1
DNA near the replication fork and synthesizes new dna as guided by the parental strand
As synthesis proceeds the forks are continually opened up to expose the template for replication
161
Since DNA polymerase III can only synthesize new DNA from 5’ to 3’, just one strand called the ____ strand will be synthesized continuously Step 2
Leading
162
After addition of an RNA primer, a DNA polymerase complex enters and moves along the template strand in the _ to_ order toward the replication fork, adding the nucleotides in the _ to _ order on the new strand Step 3
3’ to 5’
5’ to 3’
163
Lagging strand will be synthesized in a series of ___ fragments that will later be connected to into a ___ strand Step 4
Shorter
Continuous
164
Okazaki fragments Step 5
Short fragments of DNA on lagging strand
165
Lagging strand will be completed when the enzyme _____ , removes the RNA primers from the Okazaki fragments and fills the missing segments w correct complementary __ nucleotides Step 5
DNA polymerase I
DNA
166
Replacement strand is not completely bonded to the finished part of the new strand, so an enzyme, ___ makes these final ____ connections Step 6
Ligase
Phosphate- sugar
167
As replication proceeds, one newly synthesized strand ____ down
Loops
168
169
When forks have gone full circle, a termination site shuts …
Replication down
The 2 circular daughter molecules remain connected briefly but are nicked and separated by helicase
170
171
How do cells proofread
DNA polymerase III elongates the molecule, can also detect incorrect, un matching bases; excise them and replace them w the correct base
DNA polymerase I is also involved in proofreading the molecule and repairing damaged DNA
172
Master code of DNA is first used to synthesize RNA via a process called ___ , and the information contained in the RNA is then used to produce proteins in a process known as ¥__
Transcription
Translation
173
What is a gene a sequence of?
Nucleotides that code for proteins
174
DNA exists in the order of groups of three consecutive basis, design designated as ___ or ___, on one DNA strand
Triplets
Codons
175
What does each triplet represent a code for?
Amino acids
176
When the triplet code is transcribed in translated it dictates the type and order of amino acids in a
Polypeptide chain
177
The order of triplets directs, a protein’s primary structure, the order and type of ___ ___ in the chain
Amino acids
178
What contributes significantly to the phenotype by functioning as enzymes structural molecules
Proteins 
179
All types of RNA are formed through___ of a DNA gene, but only___ is further translated into protein
Transcription
mRNA
180
Messenger RNA mRNA
Transcribed the version of a structural gene or gene in DNA
Message of triplets called codons
181
Transfer RNA
Complementary copies of specific regions of DNA
Contain sequences of bases that form hydrogen bonds with complementary sections in the same tRNA strand
The molecule bend itself into hairpin loops, giving the molecule, a secondary clover leaf structure that folds even further into a complex three dimensional helix
Translator that converts RNA language into protein language 
182
What does the bottom loop of tRNA expose?
Anticodon that both designate the specificity of the tRNA and compliments mRNAs codons
On the opposite side of the molecule is a binding site for the amino acid that are specific for the TRNA anticodon
183
For each of the 20 amino acids, there is at least one specialized type of ___ to carry it finding of amino acid to its specific tRNA requires a specific enzyme that can correctly match each TRNA with its amino acid 
tRNA
184
The prokaryotic ribosome is a particle composed of tightly packaged___ and protein
rRNA
185
186
The RNA component of the ribosome is an extensive____ molecule
Polynucleotide it forms complex three dimensional figures that contribute to the structure and function of ribosome
187
The interactions of proteins and RNA create the two subunits of the ribosome that engagw in final____ of the genetic code
Translation
188
What is transcription guided by?
Special codes on DNA itself (mRNA)
189
What enzyme is responsible for a RNA molecule to be synthesized using the code on DNA as a guide or template?
RNA polymerase
190
Does RNA polymerase work alone
Yea it does not require a helicase it combined to DNA and unwind it as well as synthesize RNA
191
192
What are the three stages of transcription?
Initiation, elongation and termination
193
What does initiation of transcription require?
The RNA polymer raises to recognize a region on a gene called the promoter region
194
What does the promoter region consist of in in initiation of transcription?
Two sets of DNA sequences located just before the initiation site
Provide the position for initial binding of the RNA polymer
195
What special protein molecule guides that are polymerase to the correct position of the promoter
Sigma factor
196
What does RNA polyamory separate in transcription?
Separate the two strands of the DNA helix informs an open bubble for transcription 
197
What does the bubble and transcription serve as?
Serves at the space where the nucleotides of mRNA will actually be assembled
198
The__ made by transcription of the template strand is a message for the correct sequence of amino acids that will be linked together during translation
mRNA
199
The non-template sometimes called the coding strand because the sequence is the same order as the
mRNA
200
As elongation proceeds, the polymer moves the transcription bubble where
Forward exposing self sequence sections of DNA. It brings in nucleotides that are complementary to the DNA template and continues to assemble the mRNA strand.
It moves in the 5 to 3 direction
201
What happens in termination of transcription
The polymer recognizes a site on DNA near the end of the gene that signals of separation and release of the completed mRNA, which one next translation
202
What does mRNA deliver its messaging for protein synthesis?(termination.)
Codons that are the master code for protein
203
What are the five stages of translation?
Initiation, elongation, termination and protein, folding and processing
204
In prokaryotic cells, the mRNA molecule leaves the DNA transcription site and is transported directly to
Ribosomes
205
What cell units are specifically assembled in a way that forms sites to hold the__ and ___ (translation)
mRNA
tRNA
206
The small sub unit of ribosome binds to the five end of the MRA and provide molecules to initiate
Translation
207
The larger sub unit holds the tRNA’s and is actively involved in peptide bond formation by means of a special Bible design, which is a RNA based
Catalyst
208
Small Sub unit of the ribosome binds at a specific site on the mRNA and places the(translation)
Start code on
Incorrect alignment with the P site
209
With the mRNA message in place of the assembled ribosome, the next step in translation involves entrance of___ with their amino acids
tRNAs
210
The step in which the complementary tRNA meets with the MRA code is guided by the two sides on the large side unit the ribosome called the___ and ___
P site (left )
A site(right)
211
What does P site and a site accommodate
tRNA
212
What is redundancy or degeneracy?
A particular amino acid can be coded for by more than one codon
213
The correct tRNA enters the___ and binds to the ___ __ presented by the M
P site
Start codon
214

215
216
Elongation begins with the filling of the _ site by second __ (translation)
A
tRNA
217
218
The entry of into the A site brings the two adjacent tRNA’s in favorable proximity for a peptide bond to form between the amino acids they carry
tRNA 2
219
What is translocation in elongation?(translation)
And I’m directed shifting of the ribosome to the next position on the mRNA strand, which causes the blank tRNA to be discharged from the ribosome at the e site
220
Where is tRNA 3 inserted as directed by the mRNA 3 codon
Site a
221
What is the role of termination codons in protein synthesis?
Termination codons (UAA, UAG, UGA) signal the end of protein synthesis by indicating 'Stop here'
## Footnote
These codons do not have corresponding tRNA and lead to the release of the polypeptide chain from the ribosome.
222
What occurs when a termination codon is reached during translation?
A special enzyme breaks the bond between the final tRNA and the finished polypeptide chain
## Footnote
This process releases the polypeptide from the ribosome.
223
What are posttranslational modifications?
Alterations necessary for proteins after synthesis, such as folding, clipping off the starting amino acid, adding cofactors, and forming quaternary structures
## Footnote
These modifications help proteins achieve their functional forms.
224
How quickly can protein synthesis occur in bacteria?
12 to 17 amino acids per second at 37°C
## Footnote
An average protein of 400 amino acids can be synthesized in less than half a minute.
225
What is a polyribosomal complex?
A structure where multiple ribosomes translate a single mRNA simultaneously
## Footnote
This allows mass production of protein molecules from the same mRNA transcript.
226
How much energy is consumed in the synthesis of an average-size protein?
Approximately 1,200 ATPs or ATP equivalents
## Footnote
Protein synthesis is energetically expensive.
227
What is the start codon in eukaryotes?
AUG
## Footnote
It codes for an alternate form of methionine compared to prokaryotes.
228
True or False: Eukaryotic protein synthesis is identical to prokaryotic protein synthesis.
False
## Footnote
While there are similarities, there are also significant differences between eukaryotic and prokaryotic protein synthesis.
229
What begins to happen to the peptide chain before it is released from the ribosome?
It begins folding into its biologically active tertiary conformation
## Footnote
This folding is crucial for the protein's functionality.
230
What is a key difference between eukaryotic and prokaryotic mRNAs?
Eukaryotic mRNAs code for just one protein, while bacterial mRNAs often contain information from several genes in series.
231
Where is DNA located in eukaryotic cells?
In the nucleus.
232
Can transcription and translation occur simultaneously in eukaryotic cells?
No, they cannot occur simultaneously due to the presence of the nucleus.
233
What must the mRNA transcript do before translation in eukaryotic cells?
It must pass through pores in the nuclear membrane and be carried to the ribosomes in the cytoplasm or on the endoplasmic reticulum.
234
How is the gene pattern in prokaryotes described?
Colinear.
235
What does it mean for a gene to be colinear?
The message can be directly read into proteins without any additional processing.
236
What are introns?
Intragenic regions within genes that do not code for protein.
237
What are exons?
Coding regions within genes that will be translated into protein.
238
Fill in the blank: Eukaryotic genes are not _______ due to the presence of introns.
colinear
239
True or False: Eukaryotic genes contain only coding regions.
False.
240
What are exons and introns in a gene?
Exons are the recognizable coding regions, while introns are non-coding segments represented by nonsense letters.
241
What is a split gene?
A discontinuous genetic structure that requires further processing before translation.
242
What is pre-mRNA?
The initial transcript produced from the entire gene, containing both exons and introns.
243
What is the role of the spliceosome?
An RNA-protein complex that recognizes exon-intron junctions and performs RNA splicing.
244
What happens during RNA splicing?
Introns are excised, and exons are joined end to end to produce a mature mRNA strand.
245
What is the function of reverse transcriptase?
An enzyme that converts RNA into DNA.
246
What are endonucleases?
Enzymes that can snip DNA and allow insertions and deletions into the DNA sequence.
247
What is the significance of introns in human DNA?
Human DNA has an average of 8 introns per gene, representing a significant percentage of the DNA in chromosomes.
248
What is alternative splicing?
A process that provides greater flexibility in creating alternative versions of genes.
249
What is an operon?
A section of DNA containing one or more structural genes and a corresponding operator gene that controls transcription.
250
What are the two categories of operons?
Inducible and repressible operons.
251
How are inducible operons regulated?
They are turned on by the substrate of the enzyme for which the structural genes code.
252
What is a repressible operon?
An operon that is turned off by the product synthesized by the enzyme.
253
What is the lactose operon?
A well-understood model for inducible gene regulation in bacteria, specifically in Escherichia coli.
254
What are the three important features of the lactose operon?
* The regulator, which codes for a repressor protein
* The control locus, which includes the promoter and operator
* The structural genes that code for enzymes needed for lactose metabolism.
255
Who first described the lactose operon?
François Jacob and Jacques Monod in 1961.
256
True or False: The lactose operon is turned off when lactose is present.
False.
257
Fill in the blank: The _______ operon is an example of an inducible operon.
lactose
258
What is the role of the operator in an operon?
Acts as an on/off switch for transcription.
259
What is the structural locus in the lac operon made up of?
Three genes, each coding for a different enzyme needed to catabolize lactose
## Footnote
The enzymes include P-galactosidase and permease.
260
What does P-galactosidase do?
Hydrolyzes lactose into its monosaccharides
261
What is the role of permease in the lac operon?
Brings lactose across the cell membrane
262
Where are the promoter, operator, and structural components located in the lac operon?
Adjacent to one another, while the regulator can be at a distant site
263
What is the normal state of the lac operon in the absence of lactose?
Off mode, does not initiate enzyme synthesis
264
What key protein maintains the lac operon in the off mode?
Repressor protein
265
What is the nature of the repressor protein in the lac operon?
Allosteric, meaning its activity can be altered
266
What happens to the operator when lactose is absent?
The repressor protein interacts with the operator, distorting it into a loop configuration
267
How does the repressor protein affect RNA polymerase activity?
Blocks access of RNA polymerase to the DNA of the operator, preventing transcription
268
What triggers the lac operon to turn on?
The binding of lactose to the repressor protein
269
What occurs when lactose binds to the repressor protein?
It causes a shape change that dislodges the repressor from the operator segment
270
What is produced when the structural genes of the lac operon are transcribed?
A single unbroken transcript coding for all three enzymes
271
What is considered an inducer in the context of the lac operon?
Lactose
272
What happens when lactose is depleted in the environment?
The repressor regains its active shape and binds to the operator, locking it
273
What is the preferred carbon source for bacteria, and why?
Glucose, because it can be used immediately in growth
274
What type of operon is the lac operon?
Inducible operon
275
What is a repressible operon?
An operon that is normally in the on mode and turned off when the product is no longer required
276
What role does excess product play in a repressible operon?
Acts as a corepressor that slows transcription
277
Under what conditions is the arg operon set to on?
When a cell is consuming large amounts of arginine
278
What happens to the repressor in an active cell synthesizing arginine?
The repressor remains inactive because there is too little free arginine to activate it
279
What is the initial state of the arg operon when arginine is being actively synthesized?
On
280
What are mutations?
Alterations in the genetic code that can affect genetic expression and lead to variations in organisms.
## Footnote
Mutations can result in changes in physical or physiological traits, contributing to evolution.
281
What is a wild type microorganism?
A microorganism that exhibits a natural, nonmutated characteristic.
## Footnote
Wild strains serve as a baseline for studying mutations.
282
What is a mutant strain?
A microorganism that has developed a mutation.
## Footnote
Mutant strains can vary in morphology, nutritional characteristics, and other traits.
283
How can mutant bacteria be detected?
By inoculating solid media containing differential or selective agents such as metabolic substrates or antibiotics.
## Footnote
This method allows for the identification of colonies that exhibit different characteristics.
284
What is the purpose of antibiotics in media?
To act as selective agents for separating strains of bacteria that are drug resistant.
## Footnote
Antibiotics help isolate mutant strains that may have developed resistance.
285
What does the replica plating technique involve?
Exposing a culture of test microbes to a mutagen and then transferring colonies to plates with complete and incomplete media to identify mutants.
## Footnote
This technique was developed by Joshua Lederberg.
286
What is the role of arginine in gene regulation?
Arginine acts as a corepressor by attaching to a repressor, changing its shape and stopping transcription when no longer needed.
## Footnote
This mechanism illustrates feedback regulation in metabolic pathways.
287
What are transcription factors?
Molecules that enhance transcription of specific genes by binding to DNA grooves.
## Footnote
They play a crucial role in regulating gene expression in response to environmental stimuli.
288
What is the difference between mutation and genetic recombination?
Mutation involves alterations in the nitrogen base sequence of DNA, while genetic recombination involves the transfer of whole segments of genetic information.
## Footnote
Both processes contribute to genetic diversity but operate differently.
289
What is the significance of mutant strains in genetics?
They are useful for tracking genetic events, unraveling genetic organization, and pinpointing genetic markers.
## Footnote
Studying mutants provides insights into gene function and regulation.
290
Fill in the blank: A phenotypic change that is due to an alteration in the genotype is called a _______.
mutation
291
True or False: Eukaryotic gene control mechanisms are well understood and similar to prokaryotic operons.
False
## Footnote
Eukaryotic mechanisms are less understood and involve intrinsic regulatory segments.
292
What is the purpose of replica plating in microbial genetics?
To screen for phenotypic variants of bacteria and other microbes
## Footnote
It allows for the identification of mutant colonies by comparing growth on complete and incomplete media.
293
What are the two types of mutations based on their origin?
Spontaneous mutations and induced mutations
## Footnote
Spontaneous mutations arise randomly, while induced mutations result from exposure to mutagens.
294
What is a spontaneous mutation?
A random change in the DNA arising from errors in replication without a known cause.
295
What is the mutation frequency range observed in bacteria?
From high (10^-4 or 1 mutation per base per replication) to low (10^-9 or 1 mutation per base per replication).
296
What are mutagens?
Physical or chemical agents that damage DNA and interfere with its functioning.
297
What type of mutation can acridine dyes cause?
Frameshift mutations
## Footnote
They distort the DNA helix by inserting between adjacent bases.
298
What is a missense mutation?
A mutation that leads to the incorporation of a different amino acid into a protein.
299
What does a nonsense mutation result in?
Premature termination of protein synthesis
## Footnote
It converts a normal codon into a stop codon.
300
What is a silent mutation?
A mutation that alters a base but does not change the amino acid coded.
301
What is a frameshift mutation?
A mutation caused by insertion or deletion of bases that shifts the reading frame of mRNA.
302
What types of mutations can lead to nonfunctional proteins?
Nonsense mutations and frameshift mutations.
303
What is the primary role of DNA repair mechanisms?
To find and repair DNA that has been damaged by mutagenic agents.
304
What is photo-activation or light repair?
A mechanism that restores DNA damaged by ultraviolet radiation using visible light and DNA photolyase.
305
What is the Ames test used for?
To screen for mutagenic potential of chemicals using bacteria.
306
What is a key indicator organism in the Ames test?
A mutant strain of Salmonella enterica that has lost the ability to synthesize histidine.
307
What does a back-mutation refer to?
A mutation that reverses back to its original base composition.
308
What is the effect of insertion or deletion of bases in multiples of three?
It does not disturb the reading frame downstream from the mutation site.
309
What can cause lethal mutations?
Most mutations that lead to cell dysfunction or death.
310
What is the wild-type sequence?
The DNA sequence found in most organisms, considered the 'normal' sequence.
311
What is a mutagen?
A test agent that enhances the rate of back-mutation beyond levels that would occur spontaneously.
## Footnote
Mutagens can increase the incidence of mutations in organisms.
312
What is the Ames test used for?
To screen environmental and dietary chemicals for mutagenicity and carcinogenicity without animal studies.
## Footnote
It compares the number of back-mutated colonies on test and control plates.
313
What does a positive result in the Ames test indicate?
An increased incidence of back-mutation, suggesting that the chemical is mutagenic.
## Footnote
This is determined by comparing colony counts between control and test plates.
314
What are the potential effects of mutations?
They can be harmful, beneficial, or neutral.
## Footnote
Most mutations are harmful, but some provide adaptive advantages.
315
What happens if a mutation occurs in a gene with a single copy in haploid organisms?
The cell will likely die if the mutation leads to a nonfunctional protein.
## Footnote
This is particularly true for essential genes.
316
How do mutations contribute to evolution?
They create genetic variation, which can provide adaptive advantages under changing environmental conditions.
## Footnote
Mutations are the raw materials for evolutionary change.
317
What is natural selection?
A process where environmental pressure selects for organisms with beneficial mutations that enhance survival and reproduction.
## Footnote
This leads to the dominance of advantageous traits in a population over time.
318
What is recombination in bacteria?
An event where one bacterium donates DNA to another, resulting in a new strain.
## Footnote
This process contributes to genetic diversity in bacterial populations.
319
What are plasmids?
Small, circular pieces of DNA that replicate independently of the bacterial chromosome and often carry adaptive genes.
## Footnote
Plasmids are not essential for survival but provide advantages like drug resistance.
320
What are the three main modes of genetic recombination in bacteria?
* Conjugation
* Transformation
* Transduction
## Footnote
Each mode involves different mechanisms of DNA transfer.
321
What is conjugation?
A mode of genetic recombination where DNA is transferred from a donor cell to a recipient cell via direct contact.
## Footnote
It requires a specialized pilus for the transfer process.
322
What is transformation in bacteria?
The uptake of free DNA from the environment by a competent recipient cell.
## Footnote
Transformation does not require direct contact between donor and recipient.
323
What is transduction?
A method of genetic recombination where bacterial DNA is transferred between cells by bacteriophages.
## Footnote
This process often occurs when a bacteriophage infects a bacterial cell.
324
What is the role of the F plasmid in conjugation?
It directs the synthesis of a pilus that facilitates DNA transfer between bacterial cells.
## Footnote
Cells with the F plasmid are denoted as F* cells.
325
True or False: All mutations are beneficial to organisms.
False. Most mutations are harmful, but some can provide adaptive advantages.
## Footnote
Beneficial mutations can lead to increased survival and reproduction.
326
Fill in the blank: The Ames test compares the number of __________ on the control plate with the number on the test plate.
colonies
327
What is the role of the pilus in bacterial conjugation?
The pilus becomes part of a complex secretory system that opens a gateway between the cell walls and membranes of two cells, serving as a passageway for the plasmid.
## Footnote
The pilus facilitates the transfer of genetic material between bacteria.
328
What happens to the donor cell during the transfer of the F factor?
The donor cell makes a copy of the F factor, which is simultaneously transferred across the bridge, retaining the original plasmid.
## Footnote
This process allows the donor to remain F* and continue conjugating.
329
What is an F* cell?
An F* cell is a bacterial cell that has been changed to be capable of producing a pilus and conjugating with other cells after receiving the F factor.
## Footnote
No additional donor genes are transferred during the initial transfer.
330
Define high-frequency recombination (Hf*) donors.
Hf* donors are cells with an integrated F factor that transmit their chromosomal genes at a higher frequency than other cells.
## Footnote
This occurs because the F factor allows for more comprehensive transfer of part of the donor chromosome.
331
How long does it take to transfer an entire chromosome during conjugation?
The transfer of an entire chromosome takes about 100 minutes.
## Footnote
However, the pilus bridge is usually broken before this time, preventing full genome transfer.
332
What are R plasmids?
R plasmids are special resistance plasmids that bear genes for resisting antibiotics and other drugs.
## Footnote
They can confer multiple resistance to antibiotics such as tetracycline and chloramphenicol.
333
What is the significance of conjugation in bacterial genetics?
Conjugation allows for the transfer of genetic material, including antibiotic resistance and virulence factors, among bacteria.
## Footnote
It also provides a means to map the bacterial chromosome.
334
How do some gram-positive bacteria recombine through conjugation?
Gram-positive bacteria like Bacillus and Streptococcus recombine by transporting plasmids via specialized proteins activated during adhesion, as they lack pili.
## Footnote
The exact mechanisms are not fully understood.
335
What was the cornerstone discovery made by Frederick Griffith?
Griffith demonstrated that DNA released from dead bacterial cells could be taken up by live cells, transforming them into virulent strains.
## Footnote
This was shown through experiments with Streptococcus pneumoniae.
336
What are the two major strains of Streptococcus pneumoniae based on capsule presence?
The two major strains are the encapsulated smooth (S) strain, which is virulent, and the non-encapsulated rough (R) strain, which is non-virulent.
## Footnote
The capsule protects bacteria from phagocytic host defenses.
337
What occurs during the transformation process?
Transformation involves the uptake of free DNA from the environment by a competent bacterial cell, leading to genetic changes.
## Footnote
The new DNA can integrate into the recipient's chromosome.
338
What are competent cells?
Competent cells are bacteria capable of accepting genetic material through transformation.
## Footnote
They have special DNA-binding proteins on their cell wall.
339
What type of genes can be exchanged through transformation?
Bacteria can exchange genes for antibiotic resistance and bacteriocin synthesis through transformation.
## Footnote
This process does not require direct contact between donor and recipient cells.
340
Fill in the blank: Transformation is facilitated by special _______ proteins on the cell wall.
DNA-binding
341
True or False: The process of transformation requires direct contact between donor and recipient cells.
False
342
What is the outcome of Griffith's classic experiment?
The experiment proved that DNA released from a killed cell can be acquired by a live cell, transforming it from nonvirulent to virulent.
## Footnote
This was demonstrated by injecting mice with different strains of Streptococcus pneumoniae.
343
What is the process by which a DNA fragment binds to a surface receptor on a competent recipient cell?
Transformation
## Footnote
Transformation involves the uptake of foreign DNA by a bacterial cell, leading to genetic alteration.
344
What is the result of transformation in a recipient cell?
The recipient is transformed with a gene for synthesizing a specific product
## Footnote
In the case of S. pneumoniae, genes coding for capsule formation are brought into the cell.
345
What technique involves inserting foreign genes into a plasmid for introduction into bacterial cells?
Recombinant DNA technology
## Footnote
This technique allows for experimentation and expression of human genes in microbial cells.
346
What are bacteriophages in the context of microbial genetics?
Bacterial viruses that can serve as genetic vectors
## Footnote
Bacteriophages can carry DNA from a donor cell to a recipient cell through transduction.
347
What is transduction in microbial genetics?
The process by which a bacteriophage carries DNA from a donor cell to a recipient cell
## Footnote
This process can occur naturally in various bacteria.
348
What are the two versions of transduction?
Generalized transduction and specialized transduction
## Footnote
Generalized transduction involves random DNA fragments, while specialized transduction involves specific segments of host DNA.
349
In generalized transduction, what type of DNA is incorporated into the phage?
Random fragments of disintegrating host DNA
## Footnote
This process allows for the transfer of various genetic traits.
350
What distinguishes specialized transduction from generalized transduction?
Specific parts of the host genome are regularly incorporated into the virus
## Footnote
This specificity is due to the prior existence of a temperate prophage in the bacterial chromosome.
351
What are transposons commonly referred to as?
Jumping genes
## Footnote
Transposons can move from one part of the genome to another.
352
What did Barbara McClintock propose regarding transposons?
The existence of transposable elements in corn plants
## Footnote
Initially met with skepticism, their presence is now widely accepted in various organisms.
353
What percentage of the human genome is made up of transposons?
Nearly 45%
## Footnote
This indicates the prevalence of transposable elements in human genetics.
354
What do transposons contain that is essential for their movement?
DNA that codes for the enzymes needed to remove and reintegrate the transposon
## Footnote
Transposons can travel between chromosomal sites and plasmids.
355
What marks the point at which a transposon is inserted into the genome?
Inverted repeats
## Footnote
These sequences flank the coding region of the transposon.
356
What is a characteristic feature of transposons regarding their replication?
Some transposons replicate themselves before jumping, while others move without replicating
## Footnote
This replication can affect the copy number of transposons in the genome.
357
True or False: Transposons can be transmitted from one cell to another.
True
## Footnote
Transposons can occur in plasmids, enabling their transfer between bacterial cells.
358
What are the smallest transposons often referred to as?
Insertion elements
## Footnote
Insertion elements consist of two genetic sequences.
359
What is a retrotransposon?
A type of transposon that can transcribe DNA into RNA and then back into DNA for insertion in a new location
360
What is an integron known for?
Carrying large blocks of genetic material, especially in transmitting drug resistance
361
What are the effects of transposons on genetic language?
Can be beneficial or adverse depending on insertion location, gene relocation, and cell type
362
In bacteria, transposons are involved in which changes?
* Changes in traits such as colony morphology
* Pigmentation
* Antigenic characteristics
* Replacement of damaged DNA
* Transfer of drug resistance
363
What are the major elements of viral genetics?
Viruses consist of DNA or RNA enclosed in a protective coating and require host cell machinery for replication
364
What types of nucleic acid forms can viruses have?
* Linear
* Circular
* Segmented
365
What are the types of viral genetic material?
* Double-stranded DNA (dsDNA)
* Single-stranded RNA (ssRNA)
* Single-stranded DNA (ssDNA)
* Double-stranded RNA (dRNA)
* Retroviruses
366
Where does replication of DNA viruses occur?
In the nucleus
367
Where is the genome of most RNA viruses replicated?
In the cytoplasm
368
What is the general replication process of dsDNA viruses?
* Viral DNA enters the nucleus
* Genes are transcribed into mRNA
* mRNA is translated into viral proteins
* Viral DNA is replicated
* Mature viruses are assembled and released
369
What is the significance of oncogenic DNA viruses?
They can transform host cells into cancer cells
370
What are the types of RNA virus genomes?
* Positive-strand (+) genome
* Negative-strand (-) genome
* Positive-strand that can convert to DNA or dRNA
371
What happens during the replication of positive-strand RNA viruses?
* Translated into a large protein
* Cleaved into functional units
* Negative strand synthesized as a template for new positive strands
372
What is unique about retroviruses?
They synthesize DNA from their RNA genome using reverse transcriptase
373
What is the role of reverse transcriptase in retroviruses?
Synthesizes a single-stranded DNA against the viral RNA template
374
What occurs when retroviral DNA becomes inserted into the host's DNA?
Cells may be transformed and produce tumors
375
What is a provirus?
When the DNA of some retroviruses is inserted into the host's DNA
376
Explain the difference between positive-strand and negative-strand viral genomes.
Positive-strand genomes can be directly translated; negative-strand genomes must be converted to positive before translation
377
Conjugation is encoded by ___ and ___
Plasmids and transposons
378
Where do transformation and transduction typically take place in
Bacteria of the same or closely related species
379
Does conjugation require direct contact
Yes
380
In gram negative bacteria, bacteria conjugation typically involve what?
Conjugation pilus(F pilus)
381
382
Transformation occurs when bacteria take up extra cellular __ and incorporate it into their ___
DNA
Genomes
383
Transformation typically occurs when?
When one bacterial lyses , in which it releases its genetic contents and then another bacterium comes by and acquires it
384
What is recombination
Rearrangement of donor and recipient genomes into new, hybrid genomes
Result in new phenotypes
385
386
What is transferred during transduction
DNA transferred from one cell to another by a bacteriophage
Microbiology
flashcards
Decks in class (36)
# Cards
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Chemistry & Biochemistry49
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Ch 8 Metabolic109
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Ch. 13 Microbes131
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Ch, 4 Prokaryotes54
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Midterm Prep214
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Ch 189
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Ch. 2104
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Ch. 489
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Practice Test140
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Scientific Disease Names10
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Euk Vs Prok167
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DNA Rep27
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Lab Practicum19
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Ch. 5 Eukaryotes245
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Ch. 6147
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Ch. 9386
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Test 2 Review132
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#11-51 Cards31
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Ch. 7285
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Ch. 11349
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Ch. 12415
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Extra 12450
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Lab Review128
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Lec 3 Review64
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Ch 1456
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Disease Cards 21-28, 52-6825
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Disease Card Quiz177
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Ch. 15315
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Ch. 16319
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Final Study Guide174
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#10-20137
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#21-31169
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#32-43155
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#44-54160
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#55-68211
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Ch 1748
