Zheng Exam 1

Question 1

UV radiation produces what two pyrimidine dimers?

Answer 1

5, 6 cyclobutane

6-4 photoproduct

Question 2

UV radiation direct effect

Answer 2

cross-linking of any sugar and base residues that are close to each other

Question 3

2-Aminopurine (2-AP) pairs with

Answer 3

cytosine instead of thymidine, therefore causes mutation.

Question 4

5-bromouracil is an analog of what?

Answer 4

thymidine

Question 5

5-bromouracil in keto vs enol phase?

Answer 5

When it is in the keto state, 5’-bromouracil pairs correctly with adenine.

However, when it is in the enol state, it pairs with guanine instead

Question 6

Deamination of adenine produces

Answer 6

hypoxanthine

Question 7

Hypoxanthine pairs with what?

Answer 7

cytosine instead of thymidine

Question 8

Deamination of cytosine

Answer 8

uracil

Question 9

Uracil pairs with

Answer 9

adenine instead of guanine

Question 10

Deamination of guanine produces

Answer 10

xanthine

Question 11

xanthine pairs with

Answer 11

benign modification because it pairs with cytosine.

Question 12

important mutation caused by deamination is

Answer 12

C > T mutation.

Question 13

Why is C->T deamination so dangerous?

Answer 13

Cytosine is the target in DNA methylation. In bacterial cells, DNA methylation helps the host distinguish its own DNA from invading foreign DNA.

Question 14

O6-methyl-Guanine, which pairs with

Answer 14

T

Question 15

O4 methyl thymidine, which pairs with

Answer 15

G

Question 16

most mutagenic lesion caused by reactive oxygen is 8-oxo guanine which pairs with

Answer 16

A instead of C

Question 17

Intercalators

Answer 17

causes insertion or deletion mutations during DNA replication

Question 18

aflatoxins which forms aduct with N- 7 of guanosine to cause

Answer 18

G:C >T:A mutation.

Question 19

Photoreactivation repairs what type of mutation and uses what enzyme?

Answer 19

photolysase

FADH2 then absorbs energy from visible light.

Question 20

X-Rays

Answer 20

can break the backbone or the phosphodiester bond of DNA, therefore causes deletions of various sizes.

Question 21

Transposons

Answer 21

DNA elements that hop or transpose from one location in DNA to another, or from one DNA molecule to another.

Question 22

Insertion Sequence

Answer 22

IS element contains only the gene for transposition (transposase)

Question 23

Composite transposons

Answer 23

Tn9 or Tn10 composite transposon. The central region often contains a gene for antibiotic resistance

Question 24

TnA/Tn3 family of transposons

Answer 24

contains the gene for transposase, and another gene encoding a resolvase that is also required for transposition

Question 25

Resolution Site

Answer 25

On TnA/Tn3 family: resolution site and resolvase mediate site specific recombination during the transposition of the transposons

Question 26

Tn3 family transposon also carries a gene for antibiotic resistance for what?

Answer 26

ampicillin resistance gene

Question 27

TnA/Tn3 family transposons are transposed by

Answer 27

replicative transposition

Question 28

nonreplicative or cut-and-paste mechanism for transposition who uses it and what is it?

Answer 28

IS and composite transposons
transposon is cut out or removed from its original location, and transferred to a new target location. So there is no longer a transposon at the original site.

Question 29

What is replicative transposition

Answer 29

After replication the 2 copies of the transposons line up at the resolution sites and resolvase mediates site-specific recombination between the res sites. This releases a copy of the transposon to the donor and target DNA, respectively.