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Genetics > Lecture--Chapter 13 > Flashcards

Lecture--Chapter 13 Flashcards

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Biology 101 flashcards
1
Q

DNA strands are _____ and _____.

A

complementary; antiparallel

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2
Q

template strand specifies its complement

A

Chargaff’s rule

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3
Q

DNA strands have a ____ phosphate end and ____ OH end, replication is _____.

A

5’; 3’; directional

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4
Q

The two DNA strands separate, with each strand used as a template for synthesis of _____.

A

daughter strands

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5
Q

Replication is _____.

A

semi-conservative

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6
Q

Steps of bacterial replication:

A
  1. initiation
  2. elongation
  3. termination
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7
Q

Initiation of DNA replication starts at the ______.

A

origin of replication (oriC)

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8
Q

site where parental DNA strands have separated and new daughter strands are being made

A

replication fork

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9
Q

Elongation and ___ of new DNA.

A

synthesis

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10
Q

Replication is _____.

A

bidirectional

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11
Q

replication forks meet on opposite side of the circle and chromosomes separate

A

termination

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12
Q

motifs that bind proteins

A

sequence “boxes”

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13
Q

controls timing of replication

A

GATC methylation

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14
Q

Initiation of DNA replication: _____ initiators, separation of ____ region.

A

dnaA protein; AT-rich

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15
Q

Initiation of DNA replication: Binding of _____, establishing the _____.

A

helicase; 2 replication forks

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16
Q

Initiation of DNA replication: ____ and other proteins bind and unwind DNA.

A

DNA helicase

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17
Q

Initiation of DNA replication: ____ generates positive supercoiling ahead of each replication fork.

A

DNA helicase

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18
Q

Initiation of DNA replication: _____ travels ahead of the helicase and relieves positive supercoils.

A

DNA gyrase (topoisomerase II)

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19
Q

Initiation of DNA replication: ______ bind to the separated strands to keep them apart.

A

single-strand DNA binding proteins

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20
Q

enzymes that copy DNA

A

DNA polymerases

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21
Q

the primary polymerase of replication

A

DNA polymerase III (DNA Pol III)

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22
Q

has a role in “lagging strand” replication

A

DNA polymerase I (DNA Pol I)

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23
Q

DNA polymerases are:

A
  1. primer dependent
  2. directional
  3. processive
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24
Q

DNA polymerases: only can add nucleotides to a primer

A

primer dependent

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25
Q

DNA polymerases: can only synthesise 5’ to 3’

A

directional

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26
Q

DNA polymerases: remain on the strand and catalyse consecutive reactions

A

processive

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27
Q

___ enters catalytic site

A

dNTP

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28
Q

Base pairing according to _____ rule.

A

AT/GC

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29
Q

A phosphodiester bond forms between:

A

5’-P of entering dNTP and 3’-OH of the sugar of the previous deoxynucleotide

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30
Q

Outer 2 phosphates of a phosphodiester bond are ____.

A

released

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31
Q

occurs at the replication fork

A

elongation

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32
Q

part of elongation: binds to ssDNA, synthesises short complementary RNA strands

A

primase

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33
Q

part of elongation: complex of helicase, primase, and Pol III.

A

replisome

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34
Q

part of elongation: short, newly synthesised DNA fragments that are formed on the lagging template strand

A

Okazaki fragments

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35
Q

Elongation: DNA Pol III: On leading strand, moves continuously towards the ____ and covalently bonds the next ____.

A

replication fork; nucleotide

36
Q

Elongation: DNA Pol III: On lagging strand, periodically releases the strand, then reforms ____ at replication fork.

A

replisome

37
Q

Elongation: DNA Pol III: adds ~___ nucleotides per second.

A

400

38
Q

Elongation: DNA Pol I: Removes RNA primers by ____ activity.

A

5’–3’ exonuclease

39
Q

Elongation: DNA Pol I: fills in segment with ___

A

DNA

40
Q

Elongation: DNA Pol I: ____ makes final seal.

A

DNA ligase

41
Q

Termination: termination sequences on chromosome, opposite oriC.

A

Ter

42
Q

Termination: proteins bind to ___.

A

Tus (termination utilisation substance)

43
Q

Termination: Replication forks stop when they encounter ___.

A

Tus

44
Q

Termination: ____ dissociates, ____ seals the new strands.

A

replisome; DNA ligase

45
Q

2 intertwined DNA molecules

A

catenenes

46
Q

DNA gyrase ___ the molecules.

A

decatenates

47
Q

DNA synthesis has very high ____, 1 error per 108 bases.

A

fidelity

48
Q

Mismatched ___ is unstable.

A

base pairing

49
Q

DNA Pol III has 3’ to 5’ exonuclease activity

A

proofreading

50
Q

General features of Eukaryotic DNA replication: more complex, though includes many of the same ____.

A

enzymes

51
Q

General features of Eukaryotic DNA replication: Eukaryotic chromosomes are large, linear, and packed in ____.

A

nucleosomes

52
Q

General features of Eukaryotic DNA replication: Multiple ____ per chromosome.

A

origins of replication

53
Q

Numerous polymerases with specialised roles

A

eukaryotic DNA polymerases

54
Q

catalyse by-pass segments around damaged DNA

A

lesion-replicating polymerases

55
Q

Elongation: removes the RNA primers

A

flap endonuclease

56
Q

Elongation: ___ fills in the gap.

A

DNA pol delta

57
Q

repetitive tandem arrays of 12-16 at the ends of chromosomes

A

telomeres

58
Q

Importance of telomeres: The ___ end cannot be otherwise replicated.

A

3’

59
Q

Importance of telomeres: Protect the chromosome from ____, ____, or ____.

A

degradation; fusions; rearrangements

60
Q

have a 3’ overhang at the ends of chromosomes

A

telomeres

61
Q

synthesises telomeres on one strand using its own RNA template

A

telomerase

62
Q

gradually shorten, which limits cellular life-spans

A

telomeres

63
Q

the exchange of DNA between similar or identical segments is found in all species

A

homologous recombination

64
Q

Homologous recombination is best understood in ____.

A

E. coli

65
Q

In eukaryotes, homologous recombination usually occurs in ____.

A

meiosis I

66
Q

Exchange of DNA between non-sister ____ of homologous chromosomes.

A

chromatids

67
Q

Proposed by Robin Holliday in 1964 based on studies of fungi

A

The Holliday Model

68
Q

a mobile junction that forms between 4 strands of DNA

A

Holliday junction

69
Q

The Holliday junction must be ___ to restore duplex DNA.

A

separated

70
Q

The Holliday Model: homologous chromosomes align and are ____.

A

nicked

71
Q

The Holliday Model: a single strand separates from its complementary strand, and basepairs with its complement in the sister chromatid

A

strand invasion

72
Q

The Holliday Model: ______ formation between the 4 strands.

A

Holliday junction

73
Q

The Holliday Model: ____ can continue for some distance along the chromatid and form a ____. This is known as ___.

A

strand swap; heteroduplex; branch migration

74
Q

The Holliday Model: eventually another nick may stop the process and the strands are rejoined

A

resolution

75
Q

The Holliday Model: both chromatids are nicked at _____ locations.

A

identical

76
Q

The Holliday Model: The DNA strands to the ___ of the nicks invade the homologous chromosomes and attach to the strands to the ___ of the nicks.

A

left; right

77
Q

The Holliday Model: The Holliday junction migrates from ___ to ____. This is called ____. It creates 2 ____ regions.

A

left; right; branch migration; heteroduplex

78
Q

The Holliday Model: Two heteroduplex regions that have a few base _____.

A

mismatches (heteroduplex DNA)

79
Q

Double-Strand Break Model: both backbones are broken in one ___, and some DNA is degraded.

A

chromatid

80
Q

Double-Strand Break Model: ____ uses the other chromatid as a template for replacing lost DNA.

A

Gap repair function

81
Q

Double-Strand Break Model: Gap repair function produces 2 _____.

A

Holliday junctions

82
Q

one allele can replace the alternate allele

A

gene conversion

83
Q

Gene conversion: DNA ___ repair or DNA ___ repair.

A

gap; mismatch

84
Q

Gene conversion: DNA repair will _______.

A

correct the mismatches of heteroduplexes

85
Q

chance of sequence of the invading strand being used as a template for correction:

A

50/50

Genetics (18 decks)

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