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BIO1334 - Genetics > DNA Replication > Flashcards

DNA Replication Flashcards

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Biology 101 flashcards
1
Q

What are the 4 stages of the eukaryotic cell cycle?

A
  • G1
  • S
  • G2
  • M
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2
Q

What happens at the G1 stage?

A

Cell with chromosome in the nucleus

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3
Q

What happens at the S stage?

A

DNA replication = chromosome duplication occurs

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4
Q

What happens at the G2 stage?

A

Cell with duplicated chromosomes in nucleus

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5
Q

What happens at the M stage?

A

Mitosis = chromosome seperation

1 cell becomes 2

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6
Q

What does the chromosome state reflect?

A

The need to replicate and partition the genetic material prior to cell division

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7
Q

What are three important areas of a chromosome?

A
  • Telomeres
  • Centromeres
  • Origin of replication
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8
Q

Where do you find the telomeres on the chromosome?

A

At the ends of the chromosome

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9
Q

What is the telomeres?

A

areas of highly repetitive DNA that protect chromosome ends from DNA degradation, recommendation and end fusion with other chromosomes

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10
Q

What is the centromere on a chromosome?

A

Repetitive DNA which forms the spindle attachment sites in mitosis

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11
Q

What is the origin of replication?

A

Special sequence where duplication of the DNA begins; each chromosome will have many origins

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12
Q

At which stage is the DNA long and not condensed?

A

Interphase

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13
Q

At which stage is the chromosome condense and visible underneath a microscope?

A

Mitosis

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14
Q

Who discovered semiconservative replication?

A

Meselson and Stahl 1958

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15
Q

What is semiconservative replication?

A

Two stands of parental double helix unwind (by DNA helicase) and each specifies a new daughter strand by base-pairing rules

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16
Q

Describe Meselson and Stahl 1958 experiment:

A
  • Density ultra centrification
  • molecules of different densities with sediment at different levels in the column
  • Grew bacteria in medium N-15
  • Extracted the DNA from N-15
  • N-15 centrificated - sediment was lower than N-14
  • Shared N-15 into N-14 medium and found as replication went on DNA became more and more like N-14
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17
Q

Which is heavier N-15 or N-14?

A

N-15

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18
Q

What can we concluded from Meselson and Stahl 1958 experiment?

A

N-14 is integrated in DNA

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19
Q

What is required for DNA synthesis?

A 
-Enzyme (DNA polymerase) + Mg2+
dNTPs (dATP, dCTP, dGTP, dTTP)
-Single stranded template DNA
-Primer 3’-OH
-DNA synthesis 5’ to 3’ direction
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20
Q

What is the problem in DNA replication?

A

That there is not enough time to replicate from start to finish

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21
Q

What solves the problem of not having enough time to replicate from start to finish?

A

The origins of replication break up the time

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22
Q

What does the involvement of the origin of replication make DNA replication?

A

bidirectional

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23
Q

What does bidirectional DNA replication form?

A

Replication bubbles

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24
Q

Which is bigger eukaryotic or bacterial genome?

A

eukaryotic

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25
Q

What is the shape of the eukaryotic genome?

A

Linear

26
Q

What is the shape of the bacterial genome?

A

Circular

27
Q

Is the bacterial genome compact?

A

Yes

28
Q

What is the amount of base pairs in the human genome?

A

3000 million bp

29
Q

What is the amount of base pairs in the e.coli genome?

A

5 million bp

30
Q

Describe the replication of bacterial DNA:

A
  • Starts at the only origin of replication
  • forms a theta structure
  • 2 circular daughter DNA molecules are produced
31
Q

Describe the replication of DNA in a eukaryotic cell?

A
  • Both strands are copied at a replication fork
  • Synthesis in a 5’ to 3’ direction
  • leading strand: replicates easily as it is going in the 3’ to 5’
  • lagging strand: hard to replicate as strand is going in 5’ to 3’ so synthesis is discontinuously so gaps left
32
Q

What is caused in the DNA replication fork of the lagging strand?

A

Okazaki fragments

33
Q

Describe the lagging strand synthesis:

A
  • Primase synthesis short RNA oligonucleotides (primer) copied from DNA
  • DNA polymerases elongate RNA primers with new DNA
  • Nucleases remove RNA at 5’ end of neighbouring fragment and DNA polymerase fills the gap
  • DNA ligase connects adjacent Okazaki fragments
34
Q

What was the enzyme at the replication fork required to unwind the DNA?

A

DNA helicase

35
Q

What was the enzyme at the replication fork required to stabilise ssDNA?

A

ss-binding protein

36
Q

What was the enzyme at the replication fork required to synthesis RNA primer?

A

primase (RNA polymerase)

37
Q

What was the enzyme at the replication fork required to synthesise new DNA strand?

A

DNA polymerase

38
Q

What was the enzyme at the replication fork required to proof-read?

A

DNA polymerase

39
Q

What was the enzyme at the replication fork required to keep DNA polymerase on the DNA?

A

Sliding clamp

40
Q

What was the enzyme at the replication fork required to trim the Okazaki fragements??

A

Nuclease

41
Q

What was the enzyme at the replication fork required to join the Okazaki fragements?

A

DNA ligase

42
Q

What was the enzyme at the replication fork required for the other factors?

A

Replisome

43
Q

What does DNA helicase do?

A

Unwinds double-stranded DNA

44
Q

What does ssDNA do?

A

Prevents base-pairing until DNA polymerase arrives

45
Q

What is primase?

A

Specialised RNA polymerase

46
Q

What does sliding clamp do?

A

Attached to DNA polymerase which encircles double stranded DNA

47
Q

What does DNA ligase do?

A

joins Okazaki fragments

48
Q

What does nuclease do?

A

trims Okazaki fragments

49
Q

How is the sliding clamp loaded around the DNA?

A

By a clamp loader

50
Q

How are histones loaded onto newly synthesis DNA?

A

By histones chaperones

51
Q

What is the problem with DNA helicase unwinding DNA?

A

Causes supercoilling

52
Q

What enzyme unwinds the supercoiling?

A

Topoisomerase

53
Q

What is the total error possible in DNA replication?

A

1 in 10^10

54
Q

What is the error per nucleotides added during 5’ to 3’ polymerisation?

A

1 in 10^5

55
Q

What is the error of not being corrected in 3’ to 5’ exonucleolytic proofreading?

A

1 in 10^2

56
Q

What is the error of not being corrected in strand-directed mismatch repair?

A

1 in 10^3

57
Q

What is more accurate DNA polymerase or RNA polymerase?

A

DNA polymerase

58
Q

Why is DNA polymerase more accurate than RNA polymerase?

A

-Proof-read (incorrect nucleotides removed by 3’ to 5’ exonuclease)

59
Q

What detects incorrect base-paring in newly-synthesised DNA?

A

Mismatch repair protein MutS

60
Q

What are mutations in human Mismatch Repair genes associate with?

A

Predisposition to some cancers

BIO1334 - Genetics (24 decks)

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