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Mbg 2040 > Replication of DNA and Chromosomes > Flashcards

Replication of DNA and Chromosomes Flashcards

1
Q

What are the complementary base pairs of DNA

A

A and T
C and G

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2
Q

How many H-bonds connect C and G

A

3

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3
Q

How many H-bonds connect A and T

A

2

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4
Q

How many base pairs per turn in a double helix

A

10

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5
Q

Is a double helix left handed or right handed

A

right handed

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6
Q

Is DNA conservative, semi-conservative, or non conservative

A

semi conservative

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7
Q

What does it mean that DNA is semi-conservative?

A

when DNA replicates, one strand is conserved while a new complementary strand is made, forming a new double strand containing one conserved and one new strand

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8
Q

What is theta replication

A

replication that occurs in circular DNA

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9
Q

How does theta replication occur

A

DNA unwinds at the replication origin which produces single-stranded templates for the synthesis of new DNA, and the fork proceeds around the circle from both directions simultaneously
- this process is bidirectional**

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10
Q

What is the final product of theta replication

A

two circular DNA molecules are produced (from one original circular DNA)

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11
Q

What is rolling circle replication

A

specialized form of replication that only occurs in the F factor of some viruses

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12
Q

What is different about the origin of replication between theta replication and rolling circle replication

A

theta - origin of replication is a fork of the double stranded DNA, resulting in bidirectional replication on strands
rolling circle - replication is initiated at a break in one DNA strand and synthesis begins at the 3’ end of the break

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13
Q

How does rolling circle replication work

A

a break occurs in one strand of the circular DNA, and synthesis of new DNA occurs at the 3’ end of the break while the 5’ end is continually displaced as the strand builds
- once the new strand has synthesized around the whole circle, cleavage occurs and the newly synthesized strand replaces the old strand on the circle

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14
Q

What makes rolling circle replication repetitive/continuous

A

the 5’ end of the original strand that is eventually cleaved folds back into its circular form and can be used as a template for another set of replication

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15
Q

Is rolling circle replication bidirectional or unidirectional

A

unidirectional

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16
Q

What is linear chromosome replication

A

occurs in the linear chromosomes of eukaryotic cells: at the various origins on the linear strand, replication bubbles are formed and synthesis occurs on both strands in both directions until eventually, the various bubbles run into each other and fuse producing two identical molecules of linear DNA

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17
Q

Is linear chromosome replication unidirectional or bidirectional

A

bidirectional

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18
Q

What is special about linear chromosome replication (thinks in term of origin)

A

unlike theta and rolling circle (only have one point of origin), linear chromosome replication has various origin sites that simultaneously synthesize DNA

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19
Q

What are some requirements of DNA replication

A
  • DNA polymerase
  • dNTPs
  • single strand to be copied
  • an RNA primer
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20
Q

What direction does DNA synthesis occur

A

5’ - 3’

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21
Q

What are the features of newly synthesized DNA when compared to its original strand

A

complementary and antiparallel

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22
Q

How is a double strand of DNA held together

A

H-bonds between base pairs

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23
Q

In a replication fork, does synthesis on the two strands occur in the same direction or opposite

A

opposite

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24
Q

Why does synthesis occur in opposite directions on the two strands in a replication fork

A

because two template strands are antiparallel and synthesis is always 5’-3’ so one will synthesize in one direction, one will synthesize in the other

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25
Q

What is the issue with synthesis on the lagging strand

A

as per the name, it is lagging, so DNA synthesizes in fragments instead of one continuous strand

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26
Q

What are the fragments called created by the lagging strand

A

Okazaki fragments

27
Q

Which type of replication does not have lagging strands

A

rolling circle (only one strand being synthesized at a time)

28
Q

What are DnaA proteins in prokaryotic replication

A

initiator proteins that bind to oriC

29
Q

What does the binding of DnaA and oriC result in in prokaryotic replication

A

short stretch of DNA to unwind

30
Q

What is oriC

A

the origin of replication in prokaryotes

31
Q

What are some proteins involved in prokaryotic replication

A
  • DNA helicase
  • DNA gyrase
  • single stranded binding proteins
  • primase
  • DNA polymerase (1 and 3)
  • DNA ligase
32
Q

What is the function of helicase in prokaryotic DNA replication

A

unwinds DNA in a 5’-3’ direction only on the lagging strand ahead of replication (binds to single strand)

33
Q

What is the function of DNA gyrase in prokaryotic replication

A

a topoisomerase that makes double stranded breaks in the DNA to relieve strain that builds up from helicase activity
- binds upstream of unwinding fork to prevent torsion

34
Q

What is the function of single stranded binding proteins in prokaryotic replication

A

coats unwound single stranded DNA to keep it single stranded and prevent hairpins

35
Q

What is the function of primer in prokaryotic replication

A

synthesizes a short RNA primer that provides 3’OH end for DNA poly to begin synthesis
- primase binds directly to helicase

36
Q

What is the function of DNA polymerase 3 in prokaryotic replication

A

the main polymerase*
- has 5’-3’ poly activity and 3’-5’ exonuclease activity
- adds dNTPs to the 3’ end but can also backup to remove a nucleotide that has been misincorperated

37
Q

What is the function of DNA polymerase 1 in prokaryotic replication

A

similar to poly 3, except poly one ALSO has 5’-3’ exonuclease activity so it can remove the RNA primer and replace it with DNA

38
Q

What is the basic function of DNA poly 1

A

remove primers

39
Q

What is the basic function of DNA poly 2

A

DNA repair (restarts synthesis after repair has occurred)

40
Q

What is the basic function of DNA poly 3

A

Elongating DNA

41
Q

What is the basic function of DNA poly 4

A

DNA repair

42
Q

What is the basic function of DNA poly 5

A

DNA repair (translesion DNA synthesis)

43
Q

What protein actually synthesized the DNA

A

DNA polymerase

44
Q

What is the function of DNA ligase

A

joins Okazaki fragments together to form a continuous strand of DNA

45
Q

Where does synthesis begin in eukaryotic replication

A

autonomously replicating sequences (AT rich)

46
Q

How is helicase different in eukaryotic replication

A

binds to double-strand (instead of single)

47
Q

What is different about the Okazaki fragments and RNA primers in eukaryotic replication

A

longer RNA primers, shorter Okazaki fragments

48
Q

What phase does replication occur in eukaryotes

A

S phase

49
Q

What is different about DNA poly in eukaryotes

A

many polymerases (at least 15)

50
Q

What is the function of polymerase alpha in eukaryotes

A

primase acitvity

51
Q

What is the function of polymerase epsilon in eukaryotes

A

leading strand replication

52
Q

What is the function of polymerase delta in eukaryotes

A

lagging strand replication

53
Q

What occurs with nucleosomes in eukaryotic replication

A

need to be removed from parental DNA and reassembled on newly synthesized DNA

54
Q

What occurs with telomeres in eukaryotic replication

A

shorten with each round

55
Q

Where does origin licensing occur and what does that entail

A

means preparation for replication in eukaryotes
- occurs in the G1 phase
- replication licensing factors attach to each origin site

56
Q

What is the purpose of origin licensing

A

prep DNA for replication and prevent re-initiation of replication

57
Q

In what phase does replication begin in eukaryotes

A

S phase

58
Q

When DNA is replicated what needs to occur with histones and what protein assists in that function

A

histone proteins must also be doubled and the modifications made to DNA must also be replicated
- chaperone proteins play a key role in this function

59
Q

Why are RNA primers essential in DNA replication of circular DNA

A

circular DNA doesn’t have 3’ or 5’ ends, so the 3’ OH must be added to initiate replication in the circular DNA

60
Q

What is telomerase

A

an enzyme specific to eukaryotes that extends chromosome ends in replication cells

61
Q

How does telomerase function

A

extends the 3’ end of the chromosome without the use of a complementary template, telomerase is then removed, and synthesis takes place on the complementary strand to match the newly added nucleotides (via telomerase)

62
Q

In what cells is telomerase highly present

A

highly dividing somatic cells and germ cells

63
Q

What are shorter telomeres associated with in terms of overall health

A

diseases involving premature aging

Mbg 2040 (13 decks)

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