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Molecular biology > 3_DNA_Replication_Flashcards > Flashcards

3_DNA_Replication_Flashcards

1
Q

What is DNA replication?

A

The process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules.

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2
Q

Why is DNA replication essential?

A

It ensures that daughter cells inherit the same genetic information as the parent cell.

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3
Q

How was the process of DNA replication discovered?

A

Using radioactive labeling with ³H-thymidine in the 1960s to track newly synthesized DNA.

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4
Q

What is semi-conservative replication?

A

Each parental strand serves as a template for a new complementary strand.

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5
Q

What is bidirectional replication?

A

Replication proceeds in two directions from the origin of replication.

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6
Q

What is an origin of replication?

A

Specific DNA regions where replication begins.

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7
Q

Why are A-T rich regions found at replication origins?

A

A-T pairs have two hydrogen bonds, making them easier to separate than G-C pairs.

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8
Q

How many replication origins do bacteria and humans have?

A

Bacteria have one; humans have 30,000–50,000.

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9
Q

What is the replisome?

A

A protein complex that carries out DNA replication.

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10
Q

Name key components of the replisome.

A

Helicase, DNA polymerase, gyrase/topoisomerase, SSBPs, and primase.

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11
Q

What template is required for replication?

A

The parental DNA strand.

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12
Q

What are the substrates for DNA replication?

A

dNTPs (dATP, dCTP, dGTP, dTTP) and Mg²⁺ ions.

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13
Q

How fast does DNA replicate in bacteria?

A

1000 base pairs per second per fork.

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14
Q

How long does the S phase last in mammalian cells?

A

Approximately 8 hours.

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15
Q

Who discovered DNA polymerase?

A

Arthur Kornberg in the 1950s.

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16
Q

What are the main activities of DNA polymerase?

A

5’-3’ polymerase activity and 3’-5’ exonuclease proofreading activity.

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17
Q

What is the direction of DNA synthesis by DNA polymerase?

A

5’ to 3’.

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18
Q

What is replication fidelity?

A

The accuracy of DNA replication, with an error rate of 1 per 10 billion bases.

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19
Q

What contributes to replication fidelity?

A

DNA polymerase proofreading and mismatch repair mechanisms.

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20
Q

What is the function of primers in DNA replication?

A

They provide a starting point for DNA polymerase.

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21
Q

What synthesizes RNA primers?

A

Primase.

22
Q

What is the first step in DNA replication?

A

Initiation, where the DNA strands are separated at the replication fork.

23
Q

What happens during elongation?

A

DNA polymerase adds nucleotides to synthesize the new DNA strand.

24
Q

What completes the replication process?

A

Termination, where RNA primers are replaced and Okazaki fragments are joined.

25
Q

What is the leading strand?

A

The DNA strand synthesized continuously in the 5’ to 3’ direction.

26
Q

What is the lagging strand?

A

The DNA strand synthesized discontinuously in Okazaki fragments.

27
Q

What does helicase do?

A

Unwinds the DNA double helix.

28
Q

What is the role of topoisomerase?

A

Relieves strain caused by DNA unwinding.

29
Q

What do single-strand binding proteins (SSBs) do?

A

Stabilize unwound single-stranded DNA.

30
Q

What does ligase do?

A

Joins Okazaki fragments by forming phosphodiester bonds.

31
Q

What are telomeres?

A

Repetitive DNA sequences at chromosome ends that protect against DNA loss.

32
Q

What enzyme synthesizes telomeres?

A

Telomerase.

33
Q

What is the human telomere sequence?

A

TTAGGG.

34
Q

Where does DNA replication occur in prokaryotes?

A

In the cytoplasm.

35
Q

Where does DNA replication occur in eukaryotes?

A

In the nucleus.

36
Q

How do replication origins differ between bacteria and humans?

A

Bacteria have one origin, while humans have thousands.

37
Q

What are the three DNA polymerases in prokaryotes?

A

DNA Polymerase I, II, and III.

38
Q

Which DNA polymerase is the main replicating enzyme in prokaryotes?

A

DNA Polymerase III.

39
Q

What are the key eukaryotic DNA polymerases?

A

DNA Polymerase Alpha, Delta, and Epsilon.

40
Q

What forms at the origin of replication?

A

Two replication forks.

41
Q

What is the function of the replication fork?

A

It serves as the site where DNA is actively unwound and replicated.

42
Q

What is the melting temperature (Tm) of DNA?

A

The temperature at which half of the DNA is denatured.

43
Q

What are Okazaki fragments?

A

Short DNA fragments synthesized on the lagging strand.

44
Q

What is the role of dNTPs?

A

They are the building blocks of DNA synthesis.

45
Q

Why is telomerase active in germ cells?

A

To prevent telomere shortening and ensure full DNA replication.

46
Q

How does telomerase activity relate to cancer?

A

Increased telomerase activity is a hallmark of cancer cells.

47
Q

What prevents DNA strands from reannealing during replication?

A

Single-strand binding proteins (SSBs).

48
Q

What is the Hayflick limit?

A

The number of times a somatic cell can divide before telomere shortening stops replication.

49
Q

How long are Okazaki fragments in eukaryotes?

A

Approximately 150–200 base pairs.

50
Q

What is the overall error rate of DNA replication?

A

About 1 mutation per 10 billion bases replicated.

Molecular biology (10 decks)

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