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Biotechnology - Mid > Lec1 | DNA Replication > Flashcards

Lec1 | DNA Replication Flashcards

1
Q

What is the function of DNA replication or synthesis?

A

DNA replication or synthesis is the process by which a cell makes an identical copy of its DNA before cell division.

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2
Q

Why is DNA replication essential?

A

DNA replication is essential for the transmission of genetic information from one generation of cells to the next.

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3
Q

Where does DNA replication occur in eukaryotic cells?

A

DNA replication occurs in the nucleus of eukaryotic cells.

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4
Q

Where does DNA replication occur in prokaryotic cells?

A

DNA replication occurs in the cytoplasm of prokaryotic cells.

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5
Q

During which phase of the cell cycle does DNA replication occur?

A

DNA replication occurs in the Interphase (S phase).

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6
Q

What does it mean that DNA replication is semi-conservative?

A

Each strand in a DNA molecule serves as a template for synthesis of a new, complementary strand.

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7
Q

What is one result of the semi-conservative nature of DNA replication regarding genetic information?

A

The semi-conservative nature of DNA replication ensures that the genetic information is accurately transmitted from one generation of cells to the next.

In addition to that, semi-conservative DNA replication allows for genetic variation to arise through mutations, which can occur during DNA replication.

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8
Q

What are the three steps of DNA replication?

A
  • Initiation.
  • Elongation.
  • Termination.
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9
Q

What initiates DNA replication?

A

Pre-replication protein complexes locate the origin of replication.

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10
Q

What enzyme temporarily breaks the DNA backbone to unwind it?

A

Topoisomerase temporarily breaks the DNA backbone to unwind it.

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11
Q

What enzyme ‘unzips’ DNA by breaking hydrogen bonds?

A

Helicase ‘unzips’ DNA by breaking hydrogen bonds.

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12
Q

What molecules stabilize unwound DNA during replication?

A

Single-Stranded Binding Proteins stabilize the unwound DNA.

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13
Q

What is the ‘Y’ shaped structure formed during DNA replication?

A

The ‘Y’ shaped structure formed during DNA replication is called a replication ‘fork’.

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14
Q

How is each strand of DNA replicated during the initiation step?

A

Each strand of DNA acts as a template and is replicated differently.

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15
Q

What enzyme adds an RNA primer during elongation of the leading strand?

A

During leading strand elongation, the enzyme primase adds an RNA primer.

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16
Q

What does the RNA primer on the leading strand provide?

A

The RNA primer on the leading strand provides the starting point for synthesis by providing OH-.

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17
Q

Which enzyme adds new nucleotides to the leading strand after the primer during elongation?

A

During leading strand elongation, DNA polymerase (δ & ε) adds new nucleotides to the primer.

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18
Q

What is the direction of the synthesis of DNA for leading strand during elongation?

A

The direction of DNA synthesis on the leading strand during elongation is in the 5’ to 3’ direction.

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19
Q

How is DNA replication on the leading strand described?

A

Replication on the leading strand is described as continuous.

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20
Q

On the lagging strand, how are RNA primers added during the elongation phase?

A

On the lagging strand during the elongation phase, numerous RNA primers are added at various points along the strand.

21
Q

What are the short DNA segments synthesized on the lagging strand?

A

Short DNA segments synthesized on the lagging strand are called Okazaki fragments.

22
Q

What is the direction of synthesis for Okazaki fragments during lagging strand elongation?

A

Okazaki fragments on the lagging strand during elongation are also synthesized in the 5’ to 3’ direction.

23
Q

How is DNA replication described on the lagging strand during the elongation phase?

A

DNA replication on the lagging strand during elongation is described as discontinuous.

24
Q

During termination, what needs to happen to the Okazaki fragments created on the lagging strand?

A

During termination, Okazaki fragments on the lagging strand need to be joined together.

25
Q

What is the consequence of RNA primer removal in termination?

A

RNA primer removal leaves a gap in the DNA molecule during termination.

26
Q

During termination what fills the gaps created by removal of RNA primers?

A

During termination, DNA polymerase fills the gaps left by RNA primer removal.

27
Q

What enzyme forms phosphodiester bonds, joining Okazaki fragments into a single unified strand during termination?

A

DNA ligase forms phosphodiester bonds during termination, joining Okazaki fragments.

28
Q

At the end of replication, how does the length of the lagging strand compare to the leading strand?

A

At the end of replication, the lagging strand is shorter than the leading strand.

29
Q

Why can’t the RNA primer at the end of the lagging strand be replaced with DNA nucleotides?

A

The RNA primer at the end of the lagging strand cannot be replaced with DNA nucleotides, because there is no free 3’ OH group for DNA polymerase to add to.

30
Q

What is the consequence of not being able to replace the RNA primer at the end of the lagging strand?

A

The inability to replace the RNA primer at the end of the lagging strand leaves a gap in the newly synthesized DNA.

31
Q

Specifically, which end of the new strand is not replicated?

A

Specifically, the extreme 5’ end of the newly synthesized strand is not replicated.

32
Q

How does telomerase bind to the telomere?

A

Telomerase binds to the 3’ overhang of the telomere via its internal telomerase RNA primer.

33
Q

What is the general function of telomerase in the cell?

A

Telomerase extends the telomere.

34
Q

Which DNA polymerase is capable of extending the RNA primer?

A

DNA Polymerase -α is capable of extending the RNA primer.

35
Q

After the RNA primer is extended, what is synthesized?

A

After the RNA primer is extended, a complimentary strand is synthesized.

36
Q

Approximately how many nucleotides need to be inserted correctly during each replication of a human diploid cell?

A

Each time the DNA of a human diploid cell replicates, 6 billion nucleotides need to be inserted in the correct order.

37
Q

Are DNA polymerases always completely accurate in inserting nucleotides?

A

No enzyme is 100% efficient, and DNA polymerases will occasionally make mistakes, inserting the wrong nucleotide.

38
Q

How are the majority of errors during DNA replication corrected?

A

In the great majority of cases, errors during DNA replication are quickly corrected by the DNA polymerase itself.

39
Q

What special exonuclease activity does DNA polymerase β have?

A

DNA polymerase β has an intrinsic 3’ → 5’ exonuclease activity with a proofreading function.

40
Q

What is the function of topoisomerases in DNA replication?

A

Topoisomerases relieve the torsional strain that builds up ahead of the replication fork by breaking and re-joining the DNA strands.

41
Q

What is the role of helicase during DNA replication?

A

Helicase unwinds the double-stranded DNA molecule at the replication fork by breaking the hydrogen bonds between the two strands.

42
Q

What is the function of single-stranded binding proteins (SSBs)?

A

Single-stranded binding proteins bind to the single-stranded DNA at the replication fork and prevent the strands from re-forming into a double-stranded structure.

43
Q

What is the role of primase in DNA replication?

A

Primase synthesizes short RNA primers on each strand of DNA at the replication fork.

44
Q

What purpose do the RNA primers synthesized by primase serve?

A

RNA primers provide a starting point for DNA synthesis by another enzyme called DNA polymerase.

45
Q

What is the function of DNA polymerase (δ & ε) during DNA replication?

A

DNA polymerase (δ & ε) catalyses the addition of nucleotides to the 3’ end of the RNA primer, extending the new DNA strand in the 5’ to 3’ direction.

46
Q

What is the role of DNA polymerase α?

A

DNA polymerase α extends complementary strand from the RNA primer to help in end of replication problem.

47
Q

What role does DNA polymerase β play in DNA replication?

A

DNA polymerase β has a proofreading function that helps to maintain the fidelity of DNA replication.

48
Q

What is the function of exonuclease?

A

Exonuclease cleaves the RNA strand (primer).

49
Q

What is the role of DNA ligase?

A

DNA ligase joins the Okazaki fragments on the lagging strand together to form a continuous DNA strand.

Biotechnology - Mid (11 decks)

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