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Bio 131 > Exam 4: DNA Replication > Flashcards

Exam 4: DNA Replication Flashcards

1
Q

What are the 3 phases of DNA replication?

A
  1. Initiation
  2. Elongation
  3. Termination
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2
Q

In what direction does replication proceed?

A

Outward (bidirectionally)

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3
Q

What bonds need to be broken to separate the DNA strands without destroying them?

A

H bonds

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4
Q

What unwinds DNA?

A

DNA helicase

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5
Q

What does DNA helicase use to unwind DNA?

A

ATP

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6
Q

What is SSB?

A

Single-Stranded DNA Binding Protein

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7
Q

What is the role of SSB?

A

Prevents renaturing or formation of loops of single strands after helicase moves through

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8
Q

What does topoisomerase do?

A

It cuts and rejoins DNA

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9
Q

Why is topoisomerase critical?

A

It relieves tension in the helix

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10
Q

Is DNA topoisomerase ahead of or behind the replication fork?

A

Slightly ahead of

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11
Q

What are the two requirements for the initiation of DNA synthesis?

A
  1. There must be a nucleic acid primer
  2. DNA polymerase III adds nucleotides to the 3’ end of the primer
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12
Q

Why do a few nucleotides (primer) bond to the template strand?

A

This provides a free OH group that can combine with an incoming dNTP to form a phosphodiester bond

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13
Q

Primase is a type of …

A

RNA polymerase

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14
Q

What does primase synthesize?

A

A short RNA segment that serves as a primer

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15
Q

How many primers are needed in the leading strand?

A

1

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16
Q

DNA is synthesized as one continuous molecule in which strand?

A

Leading strand

17
Q

What is the name for how DNA is synthesized in the lagging strand?

A

Okazaki fragments

18
Q

What removes RNA primers at the beginning of each Okazaki fragment?

A

DNA polymerase I

19
Q

What joins adjacent DNA fragments?

A

DNA ligase

20
Q

What covalently links Okazaki fragments?

A

DNA ligase

21
Q

What is responsible for DNA synthesis around the replication fork?

A

Replisome

22
Q

What is the problem with the synthesis at the end of the lagging strand?

A

There is nothing to replace the last primer

23
Q

What are the regions at the ends of linear chromosomes?

A

Telomeres

24
Q

What is the role of telomerase?

A

Adds more repeating bases to the end of the lagging strand

25
Q

Telomerase has its own ___ template

A

RNA

26
Q

Which cells lack telomerase?

A

Somatic

27
Q

What happens in somatic cells as individuals age?

A

Chromosomes of somatic cells shorten

28
Q

Which enzyme proofreads and repairs mistakes?

A

DNA polymerase III

29
Q

Why can DNA polymerase III proofread and repair mistakes?

A

It has exonuclease

30
Q

What is the error rate after the proofreading process?

A

1 x 10^-7

31
Q

What is cancer?

A

Accumulation of mutations

Bio 131 (25 decks)

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