Deck 20: DNA Replication and Repair

Question 1

Which of the following explains why circular DNA, such as the chromosomes of some viruses and bacteria, appears to be twisted?

A) hybridization
B) supercoiling
C) circular DNA is Z-form
D) viral and bacterial DNA is always single stranded
E) none of the above

Answer 1

supercoiling

Question 2

What are the two components of supercoiling?

A) twist and writhe
B) twist and anti-twist
C) writhe and relaxation
D) negative supercoiling and positive supercoiling
E) single stranded and double stranded

Answer 2

twist and writhe

Question 3

Which of the following explains supercoiling in naturally occurring DNA?

A) positively supercoiled, making the helix tighter
B) positively supercoiled, making the helix looser
C) negatively supercoiled, making the helix tighter
D) negatively supercoiled, making the helix looser
E) negatively supercoiled without changing the nature of the helix

Answer 3

negatively supercoiled, making the helix looser

Question 4

What is the nucleophile in the DNA polymerase mechanism?

A) an oxygen anion on the $\gamma$ -phosphate of the dNTP
B) the oxygen on the $\beta$ -phosphate of the dNTP
C) the oxygen on the $\alpha$ -phosphate of the dNTP
D) the 5 hydroxyl on the deoxyribose
E) the 3 11ee7c72_7964_3476_ae82_235acaf16f38_TBW1044_11 hydroxyl on the deoxyribose

Question 5

If the smallest human chromosome is 4.6 * 10⁷ base pairs in size, which of the following is the best estimate of the number of Okazaki fragments resulting from its replication?

A) 300,000
B) 30,000
C) 3,000
D) 300
E) 30

Question 6

In most organisms, replication proceeds in a _____ manner from the _____.

A) bidirectional; replication origin
B) bidirectional; theta site
C) bidirectional; lagging strand
D) unidirectional; chromosome ends
E) none of the above

Question 7

Which tumor suppressor gene is found to be mutated in at least half of all human tumors?

A) BRCA1
B) BRCA2
C) retinoblastoma
D) p53
E) none of the above

Question 8

An E. coli cell actively undergoing replication contains a single replisome.

Question 9

It is generally believed that the three causes of cancer are inherited genetic variations, environmental factors, and random mutations.

Question 10

An example of a viral infection leading to cancer is ___ causing ___.

Question 11

DNA damage activates ___ and leads to an increase in the cellular concentration of ___.

Question 12

In cells with DNA damage, p53 either ___ if the DNA can be repaired or ___ if the DNA cannot be repaired.

Question 13

There are approximately ___ genes that are known to be associated with carcinogenesis but a typical cancer contains mutation in only ___.

Question 14

What reagents are required to perform PCR?

A) DNA fragment, primers flanking the region of interest, dNTPs, DNA polymerase
B) DNA fragment, primers flanking the region of interest, dNTPs, ddNTPs, DNA polymerase
C) DNA fragment, one primer, dNTPs, DNA polymerase, DNA ligase
D) DNA fragment, one primer, dNTPs, DNA polymerase, DNA endonuclease
E) DNA fragment, primers flanking the region of interest, dNTPs, DNA endonuclease

Question 15

To perform PCR, which of the following describes the reagents that must be included in the reaction mixture?

A) DNA fragment, primers flanking the region of interest, dNTPs, DNA polymerase
B) DNA fragment, primers flanking the region of interest, dNTPs, ddNTPS, DNA polymerase
C) DNA fragment, one primer, dNTPs, DNA polymerase, DNA ligase
D) DNA fragment, primers flanking the region of interest, dNTPs, DNA ligase
E) none of the above

Question 16

Describe the structure of a DNA molecule by listing six characteristics.