Lecture--Chapter 13 Flashcards Preview

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Flashcards in Lecture--Chapter 13 Deck (85):
1

DNA strands are _____ and _____.

complementary; antiparallel

2

template strand specifies its complement

Chargaff's rule

3

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

5'; 3'; directional

4

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

daughter strands

5

Replication is _____.

semi-conservative

6

Steps of bacterial replication:

1. initiation
2. elongation
3. termination

7

Initiation of DNA replication starts at the ______.

origin of replication (oriC)

8

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

replication fork

9

Elongation and ___ of new DNA.

synthesis

10

Replication is _____.

bidirectional

11

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

termination

12

motifs that bind proteins

sequence "boxes"

13

controls timing of replication

GATC methylation

14

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

dnaA protein; AT-rich

15

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

helicase; 2 replication forks

16

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

DNA helicase

17

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

DNA helicase

18

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

DNA gyrase (topoisomerase II)

19

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

single-strand DNA binding proteins

20

enzymes that copy DNA

DNA polymerases

21

the primary polymerase of replication

DNA polymerase III (DNA Pol III)

22

has a role in "lagging strand" replication

DNA polymerase I (DNA Pol I)

23

DNA polymerases are:

1. primer dependent
2. directional
3. processive

24

DNA polymerases: only can add nucleotides to a primer

primer dependent

25

DNA polymerases: can only synthesise 5' to 3'

directional

26

DNA polymerases: remain on the strand and catalyse consecutive reactions

processive

27

___ enters catalytic site

dNTP

28

Base pairing according to _____ rule.

AT/GC

29

A phosphodiester bond forms between:

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

30

Outer 2 phosphates of a phosphodiester bond are ____.

released

31

occurs at the replication fork

elongation

32

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

primase

33

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

replisome

34

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

Okazaki fragments

35

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

replication fork; nucleotide

36

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

replisome

37

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

400

38

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

5'--3' exonuclease

39

Elongation: DNA Pol I: fills in segment with ___

DNA

40

Elongation: DNA Pol I: ____ makes final seal.

DNA ligase

41

Termination: termination sequences on chromosome, opposite oriC.

Ter

42

Termination: proteins bind to ___.

Tus (termination utilisation substance)

43

Termination: Replication forks stop when they encounter ___.

Tus

44

Termination: ____ dissociates, ____ seals the new strands.

replisome; DNA ligase

45

2 intertwined DNA molecules

catenenes

46

DNA gyrase ___ the molecules.

decatenates

47

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

fidelity

48

Mismatched ___ is unstable.

base pairing

49

DNA Pol III has 3' to 5' exonuclease activity

proofreading

50

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

enzymes

51

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

nucleosomes

52

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

origins of replication

53

Numerous polymerases with specialised roles

eukaryotic DNA polymerases

54

catalyse by-pass segments around damaged DNA

lesion-replicating polymerases

55

Elongation: removes the RNA primers

flap endonuclease

56

Elongation: ___ fills in the gap.

DNA pol delta

57

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

telomeres

58

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

3'

59

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

degradation; fusions; rearrangements

60

have a 3' overhang at the ends of chromosomes

telomeres

61

synthesises telomeres on one strand using its own RNA template

telomerase

62

gradually shorten, which limits cellular life-spans

telomeres

63

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

homologous recombination

64

Homologous recombination is best understood in ____.

E. coli

65

In eukaryotes, homologous recombination usually occurs in ____.

meiosis I

66

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

chromatids

67

Proposed by Robin Holliday in 1964 based on studies of fungi

The Holliday Model

68

a mobile junction that forms between 4 strands of DNA

Holliday junction

69

The Holliday junction must be ___ to restore duplex DNA.

separated

70

The Holliday Model: homologous chromosomes align and are ____.

nicked

71

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

strand invasion

72

The Holliday Model: ______ formation between the 4 strands.

Holliday junction

73

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

strand swap; heteroduplex; branch migration

74

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

resolution

75

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

identical

76

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.

left; right

77

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

left; right; branch migration; heteroduplex

78

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

mismatches (heteroduplex DNA)

79

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

chromatid

80

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

Gap repair function

81

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

Holliday junctions

82

one allele can replace the alternate allele

gene conversion

83

Gene conversion: DNA ___ repair or DNA ___ repair.

gap; mismatch

84

Gene conversion: DNA repair will _______.

correct the mismatches of heteroduplexes

85

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

50/50