Exam 4: DNA Replication

Question 1

What are the 3 phases of DNA replication?

Answer 1

1. Initiation
2. Elongation
3. Termination

Question 2

In what direction does replication proceed?

Answer 2

Outward (bidirectionally)

Question 3

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

Answer 3

H bonds

Question 4

What unwinds DNA?

Answer 4

DNA helicase

Question 5

What does DNA helicase use to unwind DNA?

Answer 5

ATP

Question 6

What is SSB?

Answer 6

Single-Stranded DNA Binding Protein

Question 7

What is the role of SSB?

Answer 7

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

Question 8

What does topoisomerase do?

Answer 8

It cuts and rejoins DNA

Question 9

Why is topoisomerase critical?

Answer 9

It relieves tension in the helix

Question 10

Is DNA topoisomerase ahead of or behind the replication fork?

Answer 10

Slightly ahead of

Question 11

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

Answer 11

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

Question 12

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

Answer 12

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

Question 13

Primase is a type of …

Answer 13

RNA polymerase

Question 14

What does primase synthesize?

Answer 14

A short RNA segment that serves as a primer

Question 15

How many primers are needed in the leading strand?

Answer 15

1

Question 16

DNA is synthesized as one continuous molecule in which strand?

Answer 16

Leading strand

Question 17

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

Answer 17

Okazaki fragments

Question 18

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

Answer 18

DNA polymerase I

Question 19

What joins adjacent DNA fragments?

Answer 19

DNA ligase

Question 20

What covalently links Okazaki fragments?

Answer 20

DNA ligase

Question 21

What is responsible for DNA synthesis around the replication fork?

Answer 21

Replisome

Question 22

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

Answer 22

There is nothing to replace the last primer

Question 23

What are the regions at the ends of linear chromosomes?

Answer 23

Telomeres

Question 24

What is the role of telomerase?

Answer 24

Adds more repeating bases to the end of the lagging strand

Question 25

Telomerase has its own ___ template

Answer 25

RNA

Question 26

Which cells lack telomerase?

Answer 26

Somatic

Question 27

What happens in somatic cells as individuals age?

Answer 27

Chromosomes of somatic cells shorten

Question 28

Which enzyme proofreads and repairs mistakes?

Answer 28

DNA polymerase III

Question 29

Why can DNA polymerase III proofread and repair mistakes?

Answer 29

It has exonuclease

Question 30

What is the error rate after the proofreading process?

Answer 30

1 x 10^-7

Question 31

What is cancer?

Answer 31

Accumulation of mutations