Chapter 16: The Molecular Basis of Inheritance

Question 1

In his transformation experiments, what did Griffith observe?

Answer 1

Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.

Question 2

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

Answer 2

8%

Question 3

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

Answer 3

A + C = G + T

Question 4

What is meant by the description “antiparallel” regarding the strands that make up DNA?

Answer 4

The 5’ to 3’ direction of one strand runs counter to the 5’ to 3’ direction of the other strand.

Question 5

An Okazaki fragment has which of the following arrangements?

Answer 5

5’ RNA nucleotides, DNA nucleotides 3’

Question 6

Which enzyme catalyzes the elongation of a DNA strand in the 5’ → 3’ direction?

Answer 6

DNA polymerase III

Question 7

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

Answer 7

5’ A C G U U A G G 3’

Question 8

What is the function of DNA polymerase III?

Answer 8

to add nucleotides to the 3’ end of a growing DNA strand

Question 9

The leading and the lagging strands differ in that

Answer 9

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 10

A new DNA strand elongates only in the 5’ to 3’ direction because

Answer 10

DNA polymerase can only add nucleotides to the free 3’ end.

Question 11

What is the function of topoisomerase?

Answer 11

relieving strain in the DNA ahead of the replication fork

Question 12

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

Answer 12

It joins Okazaki fragments together

Question 13

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

Answer 13

single-strand binding proteins

Question 14

Which of the enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3’ end of Okazaki fragments?

Answer 14

DNA Polymerse I

Question 15

Which of the enzymes separates the DNA strands during replication?

Answer 15

Helicase

Question 16

Which of the enzymes covalently connects segments of DNA?

Answer 16

Ligase

Question 17

Which of the enzymes synthesizes short segments of RNA?

Answer 17

Primase

Question 18

Which of the following statements describes the eukaryotic chromosome?

Answer 18

It consists of a single linear molecule of double-stranded DNA plus proteins.

Question 19

Once the pattern found after one round of replication was observed, Meselson and Stahl could be confident of which of the following conclusions?

Answer 19

Replication is not conservative. It is semiconservative.

Question 20

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

Answer 20

DNA polymerase can join new nucleotides only to the 3’ end of a growing strand.

Question 21

In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules?

Answer 21

A+G = C+T

Question 22

The elongation of the leading strand during DNA synthesis

Answer 22

depends on the action of DNA polymerase.

Question 23

In a nucleosome, the DNA is wrapped around

Answer 23

histones.

Question 24

The DNA double helix model is based on whose X-ray crystallography studies?

Answer 24

Rosalind Franklin

Question 25

T or F: Each nucleotide in DNA is composed of a 5-carbon ribose sugar, a nitrogenous base, and a phosphate group.

Answer 25

False

Question 26

If the % of guanine in the DNA of an organism is 26%, what would be the % of thymine in the DNA of the organism based on Chargaff’s base pairing rule?

Answer 26

24%

Question 27

DNA in the chromosomes of eukaryotic cells is tightly coiled around which of the following structures, so that it can be packed inside the tiny microscopic nucleus of a human cell?

Answer 27

Histone Proteins

Question 28

Which of the following bases is present in RNA instead of thymine?

Answer 28

Uracil

Question 29

Which one of the following enzymes catalyzes the untwisting of the two strands of a DNA molecule when DNA replication is initiated?

Answer 29

Helicase Enzyme

Question 30

T or F: During DNA replication, multiple replication bubbles form on the single circular chromosome of a prokaryotic cell.

Answer 30

False

Question 31

Which one of the following enzymes catalyzes the joining of the Okazaki fragments of the newly synthesized lagging strand of DNA during DNA replication?

Answer 31

DNA ligase enzyme

Question 32

Which of the following enzymes proofread newly made DNA, replacing any incorrect nucleotides?

Answer 32

DNA polymerases

Question 33

To repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?

Answer 33

Nuclease, DNA polymerase, DNA ligase

Question 34

The chemical bond that joins the nitrogenous base pairs in a DNA double helix.

Answer 34

Hydrogen bond

Question 35

Single-ringed pyrimidine bases

Answer 35

Thymine, Cytosine and Uracil

Question 36

The ________ is the total genetic material of an organism.

Answer 36

genome

Question 37

Which of the following are purine bases

Answer 37

Guanine and Adenine