Question 1

Which of the following structural characteristics is most critical for the association between histones and DNA?

Accepted Answer

A)   Histones are small proteins.
B)   Histones are highly conserved (that is, histones are very similar in every eukaryote) .
C)   There are at least five different histone proteins in every eukaryote.
D)   Histones are positively charged. D

Question 2

In DNA replication in E. coli, the enzyme primase is used to attach a 5 to 10 base ribonucleotide strand complementary to the parental DNA strand. The RNA strand serves as a starting point for the DNA polymerase that replicates the DNA. If a mutation occurred in the primase gene, which of the following results would you expect?

Accepted Answer

A)   Replication would only occur on the leading strand.
B)   Replication would only occur on the lagging strand.
C)   Replication would not occur on either the leading or lagging strand.
D)   Replication would not be affected as the enzyme primase in involved with RNA synthesis. C

Question 3

Which of the following effects might be caused by reduced or very little active telomerase activity?

Accepted Answer

A)   Cells may become cancerous.
B)   Telomere lengthens in germ cells.
C)   Cells age and begin to lose function.
D)   Cells maintain normal functioning. C

Question 4

Use the figure to answer the following question.

A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in ¹⁵N medium for several generations and then transfer them to ¹⁴N medium. Which pattern in the figure would you expect if the DNA was replicated in a conservative manner?

Accepted Answer

A)   A
B)   B
C)   C
D)   D

Question 5

Semiconservative replication involves a template. What is the template?

Accepted Answer

A)   single-stranded binding proteins
B)   DNA polymerase
C)   one strand of the DNA molecule
D)   an RNA molecule

Question 6

In the polymerization of DNA, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and which of the following atoms or molecules of the last nucleotide in the polymer?

Accepted Answer

A)   the 5' phosphate
B)   C₆
C)   the 3' OH
D)   a nitrogen from the nitrogen-containing base

Question 7

In a healthy eukaryotic cell, the rate of DNA repair is typically 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?

Accepted Answer

A)   The cell can be transformed into a cancerous cell.
B)   RNA may be used instead of DNA as inheritance material.
C)   DNA replication will proceed more quickly.
D)   DNA replication will continue by a new mechanism.

Question 8

In E. coli, which enzyme catalyzes the elongation of a new DNA strand in the 5' → 3' direction?

Accepted Answer

A)   primase
B)   DNA ligase
C)   DNA polymerase III
D)   helicase

Question 9

Hershey and Chase used a DNA-based virus for their work. How might the results have been different if they had used an RNA virus?

Accepted Answer

A)   With an RNA virus, radioactive protein would have been in the final pellet.
B)   With an RNA virus, radioactive RNA would have been in the final pellet.
C)   With an RNA virus, neither sample would have had a radioactive pellet.
D)   With an RNA virus, the protein shell would have been radioactive in both samples.

Question 10

In E. coli, to repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?

Accepted Answer

A)   nuclease, DNA polymerase, RNA primase
B)   helicase, DNA polymerase, DNA ligase
C)   DNA ligase, nuclease, helicase
D)   nuclease, DNA polymerase, DNA ligase

Question 11

Which of the following characteristics would you expect of a eukaryotic organism that lacks the enzyme telomerase?

Accepted Answer

A)   a high probability of somatic cells becoming cancerous
B)   an inability to produce Okazaki fragments
C)   an inability to repair thymine dimers
D)   a reduction in chromosome length in gametes

Question 12

Which of the following investigators was (were)responsible for the discovery that in DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine?

Accepted Answer

A)   Alfred Hershey and Martha Chase
B)   Oswald Avery, Maclyn McCarty, and Colin MacLeod
C)   Erwin Chargaff
D)   Matthew Meselson and Franklin Stahl

Question 13

Which of the following statements correctly describes the difference between ATP and the nucleotides used during DNA synthesis?

Accepted Answer

A)   The nucleotides have the sugar deoxyribose; ATP has the sugar ribose.
B)   The nucleotides have two phosphate groups; ATP has three phosphate groups.
C)   ATP contains three high-energy bonds; the nucleotides have two.
D)   ATP is found only in human cells; the nucleotides are found in all animal and plant cells.

Question 14

Which of the following characteristics of eukaryotic telomeres cause them to replicate differently than the rest of the chromosome?

Accepted Answer

A)   the activity of telomerase enzyme
B)   DNA polymerase that cannot replicate the leading strand template to its 5' end
C)   gaps left at the 5' end of the lagging strand template
D)   gaps left at the 3' end of the lagging strand because of the need for a primer

Question 15

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin of replication. Which of the following events would you expect to occur as a result of this mutation?

Accepted Answer

A)   Additional proofreading will occur.
B)   No replication fork will be formed.
C)   Replication will occur via RNA polymerase alone.
D)   Replication will require a DNA template from another source.

Question 16

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?

Accepted Answer

A)   8%
B)   16%
C)   42%
D)   58%

Question 17

Which of the following molecular characteristics cause histones to bind tightly to DNA?

Accepted Answer

A)   Histones are positively charged, and DNA is negatively charged.
B)   Histones are negatively charged, and DNA is positively charged.
C)   Both histones and DNA are strongly hydrophobic.
D)   Histones are covalently linked to the DNA.

Question 18

For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to radioactively label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogen atoms. Thus, labeling the nitrogen atoms would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

Accepted Answer

A)   There is no radioactive isotope of nitrogen.
B)   Radioactive nitrogen has a half-life of 100,000 years, and the material would be too dangerous for too long.
C)   Although there are more nitrogens in a nucleotide, labeled phosphates actually have 16 extra neutrons; therefore, they are more radioactive.
D)   Amino acids (and thus proteins)  also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

Question 19

Which of the following statements correctly describes the difference between the leading and the lagging strands of DNA during DNA replication?

Accepted Answer

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.
B)   The leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end.
C)   The lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together.
D)   The leading strand is synthesized at twice the rate of the lagging strand.

Question 20