Chapter 11- DNA Replication Flashcards

1
Q

What is the correct model of DNA replication?

A

semiconservative model

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2
Q

Describe the semiconservative model

A

replicated DNA will have one old and one new strand of DNA

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3
Q

Describe the conservative model

A

the two parent strands rejoin

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4
Q

Describe the dispersive model

A

each strand is a mix of old and new

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5
Q

Describe origins of replication

A

where the two DNA strands are separated forming a “bubble”.

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6
Q

Describe the replication fork

A

the ends of the bubble where new DNA strands begin elongating.

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7
Q

Bacterial DNA is what shape?

A

circular

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8
Q

Describe helicases

A

enzymes that untwist the double helix at the replication forks

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9
Q

Describe topoisomerase

A

goes ahead of replication forks, cuts, unwinds, and rejoins DNA strands

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10
Q

Why is topoisomerase needed?

A

to keep the DNA strands from being too twisted

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11
Q

Describe single-strand binding protein

A

holds the DNA strand straight so it can be used as a template

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12
Q

What is a primer

A

a short strand of RNA that is laid down at the origin of replication

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13
Q

What is primase?

A

enzyme that lays down the primer

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14
Q

Describe DNA Polymerase III

A

adds DNA nucleotides to the 3’ end of the primer

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15
Q

The new strands grow in ________ directions.

A

opposite

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16
Q

DNA polymerases add nucleotides only to the __ ___of a strand

A

3’ end

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17
Q

a new DNA strand can elongate only in the __ to __ direction

A

5’ to 3’

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18
Q

Leading strand grows _______the origin of replication

A

in front of

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19
Q

Lagging strand grows _______ of the origin of replication

A

behind

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20
Q

Describe Okazaki fragments

A

a series of primers and new DNA segments

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21
Q

Describe DNA polymerase I

A

removes the RNA primers and replaces them with DNA nucleotides

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22
Q

Describe DNA ligase

A

connects the new DNA nucleotides

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23
Q

___ ___________ proofread DNA as it is added

A

DNA Polymerases

24
Q

________ can repair __________ based pairs or ________ DNA

A

enzymes; mismatched; damaged

25
Q

Describe nucleotide excision repair.

A

cutting out damaged DNA and replacing it with new DNA

26
Q

Describe nuclease

A

an enzyme that cuts out damaged DNA

27
Q

In nucleotide excision repair, what happens after DNA is cut out?

A
  1. DNA Polymerase adds new nucleotides2. Ligase seals the new nucleotides
28
Q

Why is DNA cut short after every replication?

A

DNA can’t be added to 5’ end new strands

29
Q

How is DNA code protected from being cut?

A

meaningless code protects the real code

30
Q

Describe telomeres

A

repetitive nucleotide sequences at the end of DNA that do not contain genes

31
Q

Describe telomerase

A

an enzyme that lengthens telomeres in gamete DNA

32
Q

Why is telomerase needed?

A

so a zygote can start off with a full set of telomeres

33
Q

If DNA replicated following the conservative model, what would the results of the Meselon-Stahl experiment look like?

A

There would be one 14N strand and one 15N strand

34
Q

If DNA replicated following the dispersive model, what would the results of the Meselon-Stahl experiment look like?

A

Each band would be a mix of 15N and 14N

35
Q

In prokaryotes, DNA replication is ___________ rather than ____________ (think direction)

A

bidrectional; unidirectional

36
Q

In prokaryotes, DNA replication begins at a specific origin site called a _______.

A

replicon

37
Q

DNA polymerase _, _, _, _ all repair damaged DNA.

A

I, II, IV, V

38
Q

DNA polymerase _, _, _ have 5’-3’ polymerization and 3’ to 5’ exonuclease activity

A

I, II, III

39
Q

3’ to 5’ exonuclease does what?

A

Proof-read synthesized base pairs

40
Q

DNA polymerase _ has 5’-3’ exonuclease activity

A

1

41
Q

What are the 3 helicase proteins in prokaryotic DNA?

A

Dna A, B, and C

42
Q

Describe DnaA

A

proteins responsible for initial steps in unwinding the helix

43
Q

Describe DnaB and DnaC

A

further opens and destabilizes the helix

44
Q

What specific type of topoisomerase reduces supercoiling?

A

DNA gyrase

45
Q

DNA polymerase III requires a primer with a free _ ________ ______.

A

3’ hydroxyl group

46
Q

Describe concurrent sythesis

A

Both DNA strands are synthesized concurrently by looping the lagging strand to invert the physical but not biological direction of synthesis

47
Q

How do polymerases proofread DNA? (what do they look for)

A

They read the amount of methylation on each strand of DNA

48
Q

Compare eukaryotic and prokaryotic chromosome and DNA structure.

A

Eukaryotic chromosomes are linear and the DNA is complexed with proteins

49
Q

___ _ and ___ _ are the major forms of the enzymes included in initiation and elongation.

A

Pol α (little Alpha); δ (little Delta)

50
Q

Describe Pol α’s and δ ‘s functions in synthesis.

A

Pol α synthesizes RNA primers during initiation on the leading and lagging strands. Polymerase switching occurs, and Pol α is replaced by δ for elongation

51
Q

Describe telomeres’ function.

A

They form hairpin loops to make chromosomes appear inert

52
Q

Why are telomeres important?

A

They prevent recombination

53
Q

Why is lagging synthesis at the end of the chromosome a problem?

A

Once RNA primer is removed, there is no free 3’ hydroxyl group from which to elongate

54
Q

What does telomerase do?

A

Direct synthesis of the telomere repeat sequence to fill the gap

55
Q

Describe the structure of telemoerse

A

A ribonucleotide protein with a RNA that serves as the template for the synthesis of its DNA compliment.