genetics > chapter 7 part 1 > Flashcards

chapter 7 part 1 Flashcards

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1
Q

central dogma

A

flow of hereditary information
DNA replication -> transcription -> RNA -> translation -> protein

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2
Q

composition of DNA nucleotides

A
  1. sugar (deoxyribose)
  2. 1/4 nitrogenous bases
  3. up to 3 phosphate groups
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3
Q

how many carbons in deoxyribose

A

5

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4
Q

where is the OH (hydroxyl) attached to deoxyribose

A

3’ carbon of deoxyribose

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5
Q

where is the H only attached to deoxyribose

A

2’ carbon

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6
Q

where is nucleotide base attached to deoxyribose

A

1’ carbon

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7
Q

where are 1-3 phosphates attached to deoxyribose

A

5’ carbon

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8
Q

2 classes of DNA nucleotides

A
  1. purine
  2. pyrimidine
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9
Q

purine

A
  • double ring
  • adenine, guanine
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10
Q

pyrimidine

A
  • single ring
  • cytosine, thymine
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11
Q

variable phosphate forms

A
  1. deoxynucleotide TRIphosphates (dNTPs)
  2. deoxynucleotide MONO phosphates (dNMPs)
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12
Q

deoxynucleotide triphosphatesw

A
  • not part of polynucleotide chain
  • act as substrate for DNA synthesis
  • dATP, dCTP
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13
Q

why are 2 phosphates removed during DNA synthesis

A

breaks high-energy phosphodiester bonds that release energy to power synthesis

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14
Q

deoxynucleotide monophosphates

A
  • part of polynucleotide chain
  • dAMP, dCMP
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15
Q

what assembles individual nucleotide into chains

A

the enzyme DNA polymerase

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16
Q

what bond does DNA polymerase form

A

phosphodiester bond

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17
Q

where does DNA polymerase form phosphodiester bond

A

between 3’ OH group of one nucleotide and 5’ phosphate of next nucleotide

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18
Q

backbone of polynucleotide chains

A

alternating sugar-phosphate backbone

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19
Q

2 rules of DNA nucleotide pairing

A
  1. bases of one strand are complementary
  2. 2 strands are antiparallel w/ respect to 3’ and 5’ ends
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20
Q

what does A pair with

A

T

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21
Q

what does G pair with

A

C

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22
Q

why are DNA strands antiparallel

A
  • brings partial charges of nucleotides into alignment
  • if parallel, nucleotides would repel each other
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23
Q

is a purine paired with a purine or pyrimidine?

A

pyrimidine

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24
Q

chemical basis of base pairing

A

formation of stable hydrogen bonds between baes on antiparallel strands

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25
how many H bonds for G/C
3
26
how many H bonds for A/T
2
27
what does base-pair stacking create
gaps between sugar phosphate backbones that partially expose the nucleotides
28
major groove
12 A wide
29
minor groove
6 A wide
30
what happens at the grooves?
DNA binding proteins can make direct contact with nucleotides
31
alternate forms of DNA
- B-form - A-form - Z-form
32
B-form DNA
- common form - 10.5 bases/turn - bases perpendicular to long axis
33
A-form DNA
- 11 bases/turn (more compact) - bases not perpendicular - dehydrating conditions (crystallization)
34
Z-form DNA
- left-handed helix - 12 bases/turn - zig-zag appearance - physiological significance unknown, observed in certain sequences near beginning of gene transcription
35
is DNA replication bidirectional or unidirectional
bidirectional
36
how many origins of replication do bacterial circular chromosomes have
one
37
how many origins of replication do eukaryotic linear chromosomes have
multiple
38
what can an autoradiograph show
origins of replication
39
how many replication origins can large eukaryotic organisms have
- thousands, separated by 40,000-50,000 base pairs
40
how many origins in human genome
10,000+ origins
41
where is replication best studied
bacteria
42
Replisomes
enzymes and proteins (2 copies of DNA pol III) involved in replication that are parts of a large complex aggregation of proteins
43
where do Replisomes assemble during synthesis
at the replication fork
44
steps of DNA replication in bacteria
1. helices breaks H bonds, topoisomerase relaxes supercoiling 2. SSB proteins prevent reannealing 3. primase synthesizes RNA primers 4. DNA pol III synthesizes daughter strand (leading/lagging) 6. DNA pol I removes/replaces nucleotides of RNA primer 7. ligase joins Okazaki fragments
45
what do certain sequences at replication origins attract
replication enzymes
46
replication origin sequence for E. coli
oriC
47
oriC
- contains 245 base pairs of A-T rich DNA - divided into 3 13-bp sequences followed by 4 9-bp sequences - 13-mer and 9-mer sequences are conserved
48
what does replication for E. coli require
replication-initiating enzymes to locate/bind to oriC censensus sequences
49
DnaA
- binds 9-mer sequences - bends DNA - breaks H bonds in A-T rich sequences of 13-mer region
50
what does DnaC carry
DnaB
51
DnaB
helicase that uses ATP energy to break H bonds of complementary baes to separate strands and unwind helix
52
what will unwinding of circular chromosome lead to
torsional stress and supercoiled DNA
53
topoisomerases
catalyze controlled cleavage and rejoining of DNA that prevents overwinding and relieves the torsional stress
54
what bond does topoisomerase break
covalent bond in backbone of one parental strand
55
Saccharomyces cervisiae (yeast)
has most fully characterized replication origin sequences
56
what are multiple origins of replication called
autonomously replicating sequences (ARS)
57
how does DNA pol III elongate DNA strands
by adding nucleotides to the 3' end of a pre-existing strand/primer
58
can DNA pol III initiate DNA synthesis on their own?
no, need primer
59
RNA primers
synthesized by specialized RNA polymerase called primase
60
primosome
enzyme machine made of primase/other proteins joined to dnaA at oriC that form the primers needed to DNA pol can begin synthesis
61
what are daughter strands synthesized by in E. coli
DNA pol III holoenzyme
62
holoenzyme
multiprotein complex in which a core enzyme (pol III) is associated with the additional components needed for full function
genetics
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