DNA Replication, Mutation and Repair - Exam Questions

Question 1

When does the S phase of the cell cycle occur?

Answer 1

Between G1 and G2 phases

Question 2

DNA synthesis occurs during which phase?

Answer 2

The S phase only.

Question 3

Roughly how long does M phase last?

Answer 3

1-2 hours

Question 4

The cell enters G0 phase:

a. when the G0 signal is received prior to entering G1 phase
b. if DNA replication fails
c. between every M phase and G1 phase in a normal cell cycle
d. if no signal is received from an external mitotic agent during G1 phase
e. as a pause between any of the other active phases.

Answer 4

d. The cell enters G0 phase if no signal is received from an external mitotic agent during G1 phase

Question 5

When DNA is replicated:

a. a single replication fork forms due to action of DNA ligase
b. two replication forks form due to action of DNA helicase
c. initiator proteins are translated at the replication origin
d. a leading fork and a lagging fork are formed
e. both DNA strands are cut by phosphodiesterase.

Answer 5

b. When DNA is replicated, two replication forks form due to the action of DNA ligase

Question 6

What are Okazaki fragments?

Answer 6

Discontinuous sections of the replicated lagging DNA strand

Question 7

How are supercoiling forces stabilised?

Answer 7

Topoisomerase

Question 8

What is DNA polymerase III responsible for?

Answer 8

Joining DNA nucleotides in prokaryotes

Question 9

The sliding clamp:

a. ensures the two DNA strands don’t break apart
b. joins DNA polymerase I to DNA polymerase III
c. links topoisomerase, DNA helicase and DNA polymerase III
d. joins DNA polymerase III to the DNA it is working on
e. serves as an error checker for DNA replication

Answer 9

d. The sliding clamp joins DNA polymerase III to the DNA it is working on.

Question 10

What is the action of DNA polymerase α?

Answer 10

Synthesis of lagging strand and primer in eukaryotes

Question 11

What is the action of DNA polymerase β?

Answer 11

DNA repair in eukaryotes

Question 12

What is the action of DNA polymerase δ?

Answer 12

Synthesis of leading strand in eukaryotes

Question 13

What is the action of DNA polymerase ε?

Answer 13

DNA repair in eukaryotes

Question 14

What is the action of DNA polymerase γ?

Answer 14

Synthesis of mitochondrial DNA

Question 15

What is the function of telomerase?

Answer 15

Creates a long sequence of short tandem repeats on DNA strand to solve the end replication paradox.

Question 16

In which cells is telomerase active?

Answer 16

Gametes

Question 17

What are indels?

Answer 17

Insertions or deletions of a small number of nucleotides

Question 18

What is the Philadelphia chromosome (abnormality of chromosome 22) an example of?

Answer 18

Translocation

Question 19

Deamination change the base C to the base..

Answer 19

U (uracil)

Question 20

UV radiation dmages DNA by causing…

Answer 20

Thymine dimers

Question 21

The mutation rate of HIV is faster than that of a eukaryotic genome by the factor of…

Answer 21

106

Question 22

Reverse transcriptase has:

a. no error-checking capacity
b. exonuclease activity in the 5’ to 3’ direction
c. exonuclease activity in the 3’ to 5’ direction
d. the ability to carry out nucleotide excision repair
e. the ability to directly repair mutated bases

Answer 22

a. Reverse transcriptase has no error-checking capacity