Dna Synthesis

Front 1

Which of the following labelled molecules would be most useful in measuring the synthesis of DNA in intact living cells? (multiple choice)
Uridine
dTTP
Thymidine
dUMP

Back 1

Thymidine

Front 2

3.) This base is in the ______ conformation? (multiple choice)
Syn
Anti

Back 2

Anti

Front 3

5.) Which of the following is (are) not characteristic of the Watson and Crick DNA double helix? (multiple choice)
The two strands wrap around each other in a right handed helix

The phosphodiester backbone is located on the exterior surface of the helix

It is susceptible to alkaline hydrolysis
It absorbs light in the ultraviolet
The strength of the bonds between the two strands is a function of the GC to AT ratio

2 and 4

Back 3

It is susceptible to alkaline hydrolysis

Front 4

6.) Chargaff’s experiments on DNA base composition demonstrated that … (multiple choice)
The ratio of A to T is always close to one
The ratio of G to C is always close to one
G always base pairs with C
A always base pairs with T
All the above
1 and 2
1 and 4
2 and 3

Back 4

1 and 2

Front 5

1.) Okazaki fragments are synthesized as part of: (multiple choice)
The leading strand
The lagging strand

Back 5

The lagging strand

Front 6

2.) Why is a topoisomerase necessary for DNA replication? (multiple choice)
To separate strands to be copied
To relieve positive supercoiling ahead of the replication fork

To position the primase on the lagging strand
To allow single stranded DNA binding protein to protect the DNA

Back 6

To relieve positive supercoiling ahead of the replication fork

Front 7

3.) A DNA helicase is necessary for DNA replication because: (multiple choice)
The strands are antiparallel
The molecule has an alpha helical structure
The stands must be separated for replication
All of the above
1 and 2
2 and 3

Back 7

2 and 3

Front 8

4.) What enzymatic activity is the error checking mechanism of DNA polymerase? (multiple choice)
5’ to 3’ exonuclease
3’ to 5’ exonuclease
5’ to 3’ endonuclease
3’ to 5’ endonuclease

Back 8

3’ to 5’ exonuclease

Front 9

5.) Which of the following biosynthetic reactions are catalyzed by a processive enzyme? (multiple choice)
DNA replication
Glycogen synthesis
Fatty acid biosynthesis
RNA synthesis
All of the above
1 and 4

Back 9

All of the above

Front 10

6.) Which of the following biosynthetic reactions are catalyzed by a processive enzyme? (multiple choice)
DNA replication
Glycogen synthesis
Fatty acid biosynthesis
RNA synthesis
All of the above
1 and 4

Back 10

All of the above

Front 11

1.) The process of mismatch repair in E. coli depends upon … (multiple choice)

An unmethylated daughter strand following replication
Recognition of methylated GATC
Action of an endonuclease
Action of Pol I
1, 2 and 3
1 and 2

Back 11

1, 2 and 3

Front 12

6.) The process of mismatch repair in E. coli depends upon … (multiple choice)

An unmethylated daughter strand following replication
Recognition of methylated GATC
Action of an endonuclease
Action of Pol I
1, 2 and 3
1 and 2

Back 12

Cytosine is occasionly deaminated

Front 13

7.) Uracil N glycohydrolase is necessary because… (multiple choice)

Back 13

2, 3 and 5

Front 14

8.) The action of a glycosylase requires the subsequent action of an ______ to complete the process of repair. (multiple choice)
Is incorporated into DNA
Causes a mutation leading to histidine dependence for growth
Causes a mutation leading to loss of histidine dependence for growth

Is metabolized by the liver extract

Back 14

Causes a mutation leading to loss of histidine dependence for growth

Front 15

10.) The liver extract is sometimes used in the Ames test because: (multiple choice)


Liver is the tissue that metabolizes drugs
Sometimes chemicals can be metabolized and become mutagenic
Some chemicals can lose their mutagenicity following metabolism

All the above
1 and 2

Back 15

All the above

Front 16

11.) Which of the following represent transversion mutations? (multiple choice)

A to T
T to A
G to A
C to T
All the above
1 and 2
3 and 4

Back 16

3 and 4

Front 17

12.) Telomeres shorten after each round of replication because: (multiple choice)
The leading strand must loop out to be replicated
The lagging strand must loop out to be replicated
An individual DNA polymerase complex is unable to function as a monomeric complex

1 and 3
2 and 3

Back 17

2 and 3

Front 18

During DNA synthesis the activity of a topoisomerase is needed. It is needed because during the course of DNA synthesis:

Back 18

b. unwinding the strands at the replication fork induces greater twisting of the two strands ahead of the replication fork. Topoisomerase action relaxes this.

Front 19

In E. coli the function of dnaA is to:

Back 19

c. bind to the sequences representing the origin of replication

Front 20

If the deoxynucleotide triphosphates serving as substrates for DNA synthesis were radioactively labelled with phosphorus 32 (32P) the phosphate which should be labelled in order for the label to be incorporated into the DNA should be at the:

Back 20

a. alpha position

Front 21

In a relaxed DNA molecule the linkage number is equal to:

Back 21

a. the number of complete turns of the double helix

Front 22

The DNA structure with the largest difference between the major and minor grooves is:

Back 22

b. B form

Front 23

DNA synthesis in E. coli can be slowed by the addition of an inhibitor of the RNA polymerase. This led to the discovery that...

Back 23

c. the primer used to initiate DNA synthesis is an RNA molecule.

Front 24

The function of a DNA helicase is to:

Back 24

c. unwind the DNA ahead of the replication fork

Front 25

The writhing number of the DNA double helix is a function of the:

Back 25

e. b and c

Front 26

The A form of DNA is found most often when:

Back 26

b. there is low humidity and a close to equivalent GC and AT content

Front 27

A topoisomerase is an enzyme which

Back 27

f. a and c

Front 28

From the E. coli origin of replication DNA synthesis proceeds:

Back 28

b. On both strands, in both directions simultaneously moving away from the origin of replication

Front 29

DNA replication proceeds in the:

Back 29

a. 5' to 3' direction

Front 30

Which of the following characteristics of DNA polymerase is (are) most important for the complete replication of the entire genome?

Back 30

f. a and b

Front 31

In E. coli in the presence of an inhibitor of RNA polymerase

Back 31

c. DNA synthesis would not occur

Front 32

In E. coli the primer which is synthesized to provide a free 3' hydroxyl for addition of nucleotides is ultimately removed by the action of:

Back 32

b. the 5' to 3' exonuclease activity of Pol I

Front 33

Synthesis of Okazaki fragments is necessary because:

Back 33

d. a and b

Front 34

The proofreading activity of DNA polymerase is attributed to

Back 34

b. the 3' to 5' exonuclease activity

Front 35

Which of the following best describes the steps necessary for the initiation of DNA synthesis in prokaryotes?

Back 35

g. a, c, d and e

Front 36

E. coli DNA polymerase I has three different enzymatic activities. Which of these is a correct description of the different activities?

Back 36

f. c, d and e

Front 37

Which of the following activities is characteristic of the telomerase enzyme?

Back 37

e. a and c