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genetics > chapter 7 part 1 > Flashcards

chapter 7 part 1 Flashcards

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Biology 101 flashcards
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
Q

how many H bonds for G/C

A

3

26
Q

how many H bonds for A/T

A

2

27
Q

what does base-pair stacking create

A

gaps between sugar phosphate backbones that partially expose the nucleotides

28
Q

major groove

A

12 A wide

29
Q

minor groove

A

6 A wide

30
Q

what happens at the grooves?

A

DNA binding proteins can make direct contact with nucleotides

31
Q

alternate forms of DNA

A
  • B-form
  • A-form
  • Z-form
32
Q

B-form DNA

A
  • common form
  • 10.5 bases/turn
  • bases perpendicular to long axis
33
Q

A-form DNA

A
  • 11 bases/turn (more compact)
  • bases not perpendicular
  • dehydrating conditions (crystallization)
34
Q

Z-form DNA

A
  • left-handed helix
  • 12 bases/turn
  • zig-zag appearance
  • physiological significance unknown, observed in certain sequences near beginning of gene transcription
35
Q

is DNA replication bidirectional or unidirectional

A

bidirectional

36
Q

how many origins of replication do bacterial circular chromosomes have

A

one

37
Q

how many origins of replication do eukaryotic linear chromosomes have

A

multiple

38
Q

what can an autoradiograph show

A

origins of replication

39
Q

how many replication origins can large eukaryotic organisms have

A
  • thousands, separated by 40,000-50,000 base pairs
40
Q

how many origins in human genome

A

10,000+ origins

41
Q

where is replication best studied

A

bacteria

42
Q

Replisomes

A

enzymes and proteins (2 copies of DNA pol III) involved in replication that are parts of a large complex aggregation of proteins

43
Q

where do Replisomes assemble during synthesis

A

at the replication fork

44
Q

steps of DNA replication in bacteria

A
  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)
  5. DNA pol I removes/replaces nucleotides of RNA primer
  6. ligase joins Okazaki fragments
45
Q

what do certain sequences at replication origins attract

A

replication enzymes

46
Q

replication origin sequence for E. coli

A

oriC

47
Q

oriC

A
  • 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
Q

what does replication for E. coli require

A

replication-initiating enzymes to locate/bind to oriC censensus sequences

49
Q

DnaA

A
  • binds 9-mer sequences
  • bends DNA
  • breaks H bonds in A-T rich sequences of 13-mer region
50
Q

what does DnaC carry

A

DnaB

51
Q

DnaB

A

helicase that uses ATP energy to break H bonds of complementary baes to separate strands and unwind helix

52
Q

what will unwinding of circular chromosome lead to

A

torsional stress and supercoiled DNA

53
Q

topoisomerases

A

catalyze controlled cleavage and rejoining of DNA that prevents overwinding and relieves the torsional stress

54
Q

what bond does topoisomerase break

A

covalent bond in backbone of one parental strand

55
Q

Saccharomyces cervisiae (yeast)

A

has most fully characterized replication origin sequences

56
Q

what are multiple origins of replication called

A

autonomously replicating sequences (ARS)

57
Q

how does DNA pol III elongate DNA strands

A

by adding nucleotides to the 3’ end of a pre-existing strand/primer

58
Q

can DNA pol III initiate DNA synthesis on their own?

A

no, need primer

59
Q

RNA primers

A

synthesized by specialized RNA polymerase called primase

60
Q

primosome

A

enzyme machine made of primase/other proteins joined to dnaA at oriC that form the primers needed to DNA pol can begin synthesis

61
Q

what are daughter strands synthesized by in E. coli

A

DNA pol III holoenzyme

62
Q

holoenzyme

A

multiprotein complex in which a core enzyme (pol III) is associated with the additional components needed for full function

genetics (37 decks)

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