CH 13: Molecular Basis of Inheritance

Question 1

The experiments of Meselson and Stahl showed that DNA __________.

Answer 1

replicates in a semiconservative fashion

Question 2

The rate of elongation of a DNA strand in prokaryotes is __________ the rate in eukaryotes.

Answer 2

much faster than

Question 3

The two strands of a DNA double helix are antiparallel. This means that __________.

Answer 3

one strand runs in the 5’ to 3’ direction and the other runs in the 3’ to 5’ direction

Question 4

What technique was most helpful to Watson and Crick in developing their model for the structure of DNA?

Answer 4

X-ray crystallography

Question 5

One strand of a double-stranded DNA molecule has the base sequence 5’-ATAGGT-3’. The complementary base sequence on the other strand of DNA will be 3’-__________-5’.

Answer 5

TATCCA

Question 6

What enzyme joins Okazaki fragments?

Answer 6

DNA ligase

Question 7

Which of the following components is required for DNA replication?

Answer 7

RNA primers

Question 8

Who is credited with discovering the structure of the DNA double helix?

Answer 8

Watson and Crick

Question 9

DNA polymerase adds nucleotides to the __________ of the leading strands and to the __________ of the lagging strands (Okazaki fragments).

Answer 9

3’ end; 3’ end

Question 10

Avery and his colleagues’ 1944 experiment showed that DNA __________.

Answer 10

was the substance that transformed the bacteria in Griffith’s experiment

Question 11

Which of the following lists is in order from the entity with the smallest genome to the entity with the largest genome?

Answer 11

Virus, bacteria, eukaryote

Question 12

The unwinding of DNA at the replication fork causes twisting and strain in the DNA ahead of the fork, which is relieved by an enzyme called __________.

Answer 12

topoisomerase

Question 13

Why were many of the early experiments on DNA carried out on viruses and bacteria?

Answer 13

All of the listed responses are correct.

Question 14

The role of DNA polymerases in DNA replication is to __________.

Answer 14

attach free nucleotides to the new DNA strand

Question 15

In DNA, the two purines are __________, and the two pyrimidines are __________.

Answer 15

adenine and guanine; cytosine and thymine

Question 16

Once the DNA at the replication fork is unwound by helicases, what prevents the two strands from coming back together to re-form a double helix?

Answer 16

Single-strand binding proteins bind the unwound DNA and prevent the double helix from re-forming

Question 17

What is the major difference between bacterial chromosomes and eukaryotic chromosomes?

Answer 17

Bacteria have a single circular chromosome, whereas eukaryotes have several linear chromosomes.

Question 18

The “beads on a string” seen in interphase chromatin are __________.

Answer 18

nucleosomes

Question 19

A scientist assembles a bacteriophage with the protein coat of phage T2 and the DNA of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have __________.

Answer 19

the protein and DNA of T4

Question 20

The incorporation of an incorrect base into a DNA molecule during replication __________.

Answer 20

can be repaired by the mismatch repair system

Question 21

During Griffith’s experiments with Streptococcus pneumoniae in mice, material from __________ bacteria transformed __________ bacteria.

Answer 21

heat-killed virulent; living nonvirulent

Question 22

The overall error rate in a completed DNA molecule is approximately __________.

Answer 22

one error per 10,000,000,000 nucleotides

Question 23

Once the DNA at the replication fork is unwound by helicases, what prevents the two strands from coming back together to re-form a double helix?

Answer 23

Single-strand binding proteins bind the unwound DNA and prevent the double helix from re-forming.

Question 24

Chargaff found that in DNA samples, __________.

Answer 24

the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1