ch 15

Question 1

Viruses ______.

Answer 1

B) use the host cell to copy themselves and make viral proteins.

Question 2

In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?

Answer 2

B) DNA contains phosphorous, whereas protein does not.

Question 3

In analysis of the nucleotide composition of DNA, which of the following will be found?

Answer 3

C) A + C = G + T

Question 4

Of the following, which is the most current description of a gene?

Answer 4

C) A DNA sequence that is expressed to form a functional product: either RNA or polypeptide.

Question 5

In the polymerization of DNA, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and _______ of the last nucleotide in the polymer.

Answer 5

C) the 3’ OH

Question 6

Within a double stranded DNA molecule, adenine forms hydrogen bonds with thymine and cytosine forms hydrogen bonds with guanine. This arrangement _______.

Answer 6

B) Permits complementary base pairing.

Question 7

Who performed classic experiments that supported the semiconservative model of DNA replication?

Answer 7

B) Meselson and Stahl

Question 8

DNA is synthesized through a process known as _______.

Answer 8

A) Semiconservative replication

Question 9

E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from the cells is centrifuged. What density distribution of DNA would you expect in this experiment?

Answer 9

D) One low-density and one intermediate-density band.

Question 10

DNA contains the template needed to copy itself, but it has no catalytic activity in cells. What catalyzes the formation of phosphodiester bonds between adjacent nucleotides in the DNA polymer being formed?

Answer 10

B) DNA polymerase

Question 11

What provides the energy for the polymerization reactions in DNA synthesis?

Answer 11

D) the deoxyribonucleotide triphosphate substrates

Question 12

(picture)
What bases will be added to the primer as DNA replication proceeds? The bases should appear in the new strand and the order that they will be added starting at the 3’ end of the primer.

Answer 12

C) A, G, A, C, G, A, C

Question 13

What is a major difference between eukaryotic DNA replication and prokaryotic DNA replication?

Answer 13

B) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have multiple origins of replication.

Question 14

A specific area of a chromosome, the following sequence of nucleotides is present where the chain opens to form a replication fork:
3’ CCTAGGCtGCAATCC 5’
An RNA primer is formed starting at the underlined T (t) of the template. Which of the following represents the primer sequence?

Answer 14

D) 5’ ACGUUAGG 3’

Question 15

The leading and the lagging strands differ in that ______.

Answer 15

A) The leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

Question 16

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

Answer 16

C) It joins Okazaki fragments together.

Question 17

Which of the following help(s) to hold the DNA strands apart while they are being replicated?

Answer 17

D) single-strand DNA binding proteins

Question 18

How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes?

Answer 18

D) It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity.

Question 19

The DNA of telomeres has been highly conserved throughout the evolution of eukaryotes. This most likely reflects _____.

Answer 19

E) A critical function of telomeres.

Question 20

What is a telomere?

Answer 20

D) The ends of linear chromosomes.

Question 21

Telomere shortening puts a limit on the number of times a cell can divide. Research has shown that telomerase can extend the lifespan of cultured human cells. How might adding telomerase affect cellular aging?

Answer 21

B) Telomerase eliminates telomere shortening and retards aging.

Question 22

In a healthy cell, the rate of DNA repair is equal to the rate of DNA mutation. When the rate of repair lags behind the rate of mutation, what is a possible fate of the cell?

Answer 22

A) The cell can be transformed to a cancerous cell.

Question 23

Researchers found E. coli that had mutation rates 100 times higher than normal. Which of the following is the most likely cause of these results?

Answer 23

C) The proofreading mechanism of DNA polymerase was not working properly.

Question 24

In humans, xeroderma pigmentosum (XP) is a disorder of the nucleotide excision repair (NER) mechanism. These individuals are unable to repair DNA damage caused by ultraviolet light. Which of the following are the most prominent types of DNA lesions in individuals suffering from xeroderma pigmentosum?

Answer 24

D) Thymine dimers

Question 25

Which one of the following is LEAST likely to cause mutations in DNA?

Answer 25

D) Light from an incandescent bulb.

Question 26

Given the damage caused by UV radiation, the kind of gene affected in those with XP is one whose product is involved with ______.

Answer 26

C) The ability to excise single-strand damage and replace it.