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Genetics > Module 5 lecture 5-9 > Flashcards

Module 5 lecture 5-9 Flashcards

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Biology 101 flashcards
1
Q

in watson and cricks report in the journal they stated

A

the pairing proposed does suggest a possible copying mechanism for genetic material; replication

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2
Q

watson and crick favored what model of DNA Replication

A

Semi-conservative

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3
Q

what models where there of DNA replication

A

semi-conservative model, conservative model, dispersive model

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4
Q

Semiconservative replication

A

one strand is used as a copy for 2 new molecules

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5
Q

conservative replication

A

he parental double helix remains
intact; both strands of the daughter double helix are newly
synthesized

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6
Q

dispersive replication

A

At completion, both strands of both
double helices contain both original and newly synthesized
material.

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7
Q

mehelson stahl experiment was used to determine

A

which type of replication occured

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8
Q

describe mehelson stahl experiment

A

-started out with “normal” DNA
-They grew it for one
generation with the heavy
isotope 15N instead of normal
14N
-

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9
Q

weight differences between N15 and N14 allowed tracking

A

N15 able to track

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10
Q

What DNA-“weight” would
you expect for any of the
three suggested models in
the first generation

A

Conservative: Two distinct bands (heavy and light).
Semi-Conservative: One intermediate band.
Dispersive: One intermediate band

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11
Q

mehelson stahl experiment control

A

e. coli grown in N14-> dna extracted from cells-> centrifuge

results N14N14 single band towards top of tube

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12
Q

mehelson stahl experiment first part

A

e. coli grown for many generation in N15 medium->Extract DNA->Centrifuge

results: 1 band of dna N15 towards the bottom

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13
Q

mehelson stahl experiment second part

A

N15 cells transfered to N14 medium->cells replicate to form first generation of daughter cells-> extract DNA-> centrifuge

Results: single band in middle of tube in between n15 and N14. meant DNA strand had both n15 and N14

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14
Q

mehelson stahl experiment third part

A

cells replicate to form second generation of daughter cells-> extract DNA-> centrifuge

results: band of hybrid N15N14, and band of N14N14

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15
Q

After growing Escherichia coli for several generations in a
medium containing 15N, they found that the DNA of the cells
was heavier than normal because

A

N15 atoms are heavier

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16
Q

what determines where it accumulates in the tube after centrifuge

A

density of DNA

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17
Q

semiconservative replication detailed model shows

A

-original double helix
-strands seperate
-complementary bases align opposite templates (A-T, C-G)
-enzymes link sugar phosphate backbone of aligned nucleotide into continuous strand

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18
Q

end result of semiconservative replication

A

2 molecules of DNA each has old strand and new strand. if layed on top of each other they should be identical.

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19
Q

Complementary base pairing produces

A

semi-conservative
replication

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20
Q

summary of semiconservative replication

A

-Double helix unwinds
-Strands separate
-Each strand acts as template for new strand
- Complementary base pairing ensures that T signals addition of A on new strand, and G signals addition of C
-Two daughter helices produced after replication

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21
Q

New daughter strands have to be synthesized from

A

free nucleotides

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22
Q

5-3 synthesis is _____ then 3-5

A

easier

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23
Q

in 5-3 there is

A

a bond made between hydroxal group on 3 carbon and incoming nucleotide phosphate group

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24
Q

DNA polymerases only works

A

5’ to 3’

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25
Q

DNA polymerase enzyme can only connect a

A

new nucleotide
to a free third carbon atom of a preceding nucleotide

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26
Q

what different abou RNA as appose to DNA

A

RNA polymerases can start from scratch

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27
Q

in dna replication there are _______ and ______ strands

A

leading and lagging

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28
Q

Leading strand is made

A

continuously in 5’->3’ direction following the moving replication
fork

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29
Q

in leading strand The initial free 3’ end is provided by

A

a short RNA prime

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30
Q

primer is made by ________

A

Primase

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31
Q

primase=

A

rna polymerase

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32
Q

lagging strand is made

A

discontinuously in form of smaller fragments

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33
Q

what are the smaller fragments in Lagging strand

A

1000 nucleotides and okazaki fragments

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34
Q

in lagging strand there are _____ fragments

A

shorter

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35
Q

Each shorter fragment is started by an

A

RNA PRIMER

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36
Q

how many okazaki fragments are there

A

2

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37
Q

After two Okazaki fragments are finished they are connected by a

A

DNA Ligase

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38
Q

what are some key enzymes involved in dna replication (6)

A

DNA helicase
Pol III
Pol I
Primase
Ligase

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39
Q

Dna helicase

A

unwinds double helix

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40
Q

polymerase III

A

produces new strands of complementary DNA

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41
Q

Polymerase I

A

fills in gaps between newly synthesized Okazaki
segments

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42
Q

Primase

A

creates RNA primers to initiate synthesis

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43
Q

ligase

A

welds together Okazaki fragments

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44
Q

how many key enzymes are involved in dna replication

A

6

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45
Q

Single-stranded binding proteins

A

keep helix open

46
Q

primary enzyme of dna synthesis

A

POL III

47
Q

what enzymes re implicated in DNA repair

A

Pol I and Pol II

48
Q

All DNA polymerase (I, II, III) have

A

3-5 prime exonuclease activity

49
Q

whats special about DNA pol i as apposed to Pol I and II.

A

Polymerase I participates in 5-3 prime exonucelase activity.

50
Q

3-5 prime exonuclease activity is involved in

A

proofreading

51
Q

DNA replication starts at

A

origin of replication

52
Q

replication bubble made using 2

A

replication forks

53
Q

lagging strand is tied together by

A

ligase enzyme

54
Q

in eukaryotes okazaki fragments are smaller. how small?

A

150 nucleotides

55
Q

how many “classic” DNA polymerases are there

A

5

56
Q

what are the 5 “classic” DNA polymerases

A

Pol a
pol s
pol e
pol y
pol b

57
Q

pol a (alpha)

A

extends RNA primer with 20 nucleotides

58
Q

pol s

A

main polymerase, when reaching next Okazaki fragment it displaces fragment and keeps synthesizing DNA

59
Q

what is the main polymerase

A

pol s

60
Q

Pol y

A

replicates mitochondrial genome

61
Q

pol B (beta)

A

does dna repair

62
Q

pol y, s, e have

A

exonucelase activity and (proofreading)

63
Q

in eukarotes Replication forks move in

A

opposite directions

64
Q

is the replication fork moves in opposite directions then

A

Replication is bidirectional

65
Q

Eukaryotic chromosomes have several hundred

A

origins of replication

66
Q

In circular chromosomes, such as E. coli, there is only how many ORIC

A

one origin of replication

67
Q

in linear chromosomes, telomeres ensure the

A

maintenance and accurate replication of chromosome ends

68
Q

Unwinding of chromosomes causes

A

supercoiling

69
Q

Errors during replication are ____

A

rare

70
Q

after errors during replication are made they are

A

immidientely corrected

71
Q

Enzymes repair ________ to DNA

A

chemical change

72
Q

Complementary strands are ______

A

redundant

73
Q

telomeres solve the

A

end problem

74
Q

unwinding of chromosomes at one location causes another location to

A

wind tightly (supercoil)

75
Q

solution to supercoil is

A

topoisomerases

76
Q

topoisomerase works by

A

cutting dna, rotate strands so not winded, then strand is rejoined by ligase.

77
Q

topoisomerase is in

A

eukaryotes and prokaryotes

78
Q

important topoisomerase in bacteria is known as

A

girase

79
Q

since complementay strands are redundant

A

basis to repair errors correctly either during or after replication

80
Q

what generates diversity

A

mutations and New combinations of already existing alleles

81
Q

how can New combinations of already existing alleles occur (3)

A

-Independent assortment of homologous chromosomes
-Crossing-over
-recombination

82
Q

Molecular Mechanism of Crossing-over first step is

A

initial cut, by spo11

83
Q

what enzyme is involved in cutting strand of chromatids

A

spo11

84
Q

non sister chromatids involved in

A

crossing over

85
Q

Molecular Mechanism of Crossing-over second step

A

exonuclease chew away from intial cuts and 3 prim single stranded tails are formed

86
Q

one of the tails from cut made will ______ another chromatid

A

invade, and takes its place

87
Q

when chromatid is invaded and strands place is taken the previous strand that was there before is

A

displaced

88
Q

displacement of strand during strand invasion forms

A

D loop

89
Q

Molecular Mechanism of Crossing-over third step

A

formation of holiday junction

90
Q

formation of holiday junction

A

2 crosses between strands of 2 different chromatids

91
Q

holiday junctions can

A

migrate.

92
Q

when holiday junctions migrate we have a

A

heteroduplex (in between holiday junctions)

93
Q

holiday junction migration moves towards

A

holiday junctions

94
Q

Whether Crossing over Occurs Depends on

A

the Resolution of Both Holliday Junctions

95
Q

if resolution of intermediates is the same there will be ______. if it is the same there is_____

A

gene conversion; crossing over

96
Q

in heteroduplex there are

A

2 chromosomes, 4 chromatids, 4 alleles

97
Q

after heteroduplex form and repair there are

A

Mismatch repair no. 1 and 2
Mismatch repair no. 3 and 4

98
Q

Mismatch repair no. 3 and 4

A

leads to allele frequency changes

99
Q

Mismatch repair no. 1 and 2

A

regenerate original allele
combinations

100
Q

how many chromatids are involved in crossovers

A

2

101
Q

what happens to the 2 unused chromatids in crossovers

A

remain same

102
Q

If original was AA BB after mismatch repair, no. 3 and 4 result in
genotypes ABBB or AAAB

A

Allele ratios change from 2:2 to 3:1 or 1:3

103
Q

when allelic changes occur as a result of heteroduplex resolution we get

A

gene conversion

104
Q

What Happens in Heteroduplexes?

A

-If the two strands are not identical we end up with a base pair mismatch in the heteroduplex

105
Q

The mismatch will be fixed by _______

A

cellular enzymes

106
Q

how do cellular enzymes fix mismatches

A

cut out the wrong base and replace it

107
Q

But how does the enzyme know which base has to be replaced

A

enzymes recognize pairing isnt correct

108
Q

how does heteroduplex work

allele A- ATATCG. allele C- ATCTCG
AATAGC TAGAGC

after reombination what would happened

A

the strands are similar so there could be a mixmatch in the dna bases

109
Q

mismatches can be repairs to

A

A/A or B/B repairs. original A allele. and B/B means original B allele

110
Q

heteroduplex can make

A

mismatch pairs.

Genetics (29 decks)

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