Practice Questions

Hershey and Chase set out to determine what molecule served as the unit of inheritance. They completed a series of experiments in which E. coli was infected by a T2 virus. Which molecular component of the T2 virus actually ended up inside the cell?

A) DNA

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?

Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

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?

B) With an RNA virus, radioactive RNA would have been in the final pellet.

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?

C) 5' A C G U U A G G 3'

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

C) A + G = C + T

Within a double-stranded DNA molecule, adenine forms hydrogen bonds with thymine, and cytosine forms hydrogen bonds with guanine. What is the significance of the structural arrangement?

C) It permits complementary base pairing.

What is meant by the description "antiparallel" regarding the two strands that make up the DNA double helix? A) Base pairings create unequal spacing between the two DNA strands. B) One strand contains only purines and the other contains only pyrimidines. C) The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand. D) The double helix structure of DNA creates nonparallel strands.

C) The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

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

C) 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.

Referring to the figure, what bases will be added to the primer as DNA replication proceeds? A) 5' C,A,G,C,A,G,A 3' B) 3' T,C,T,G,C,T,G 5' C) 3' G,T,C,G,T,C,T 5' D) 5' A,G,A,C,G,A,C 3'

D) 5' A,G,A,C,G,A,C 3'

In an analysis of the nucleotide composition of a molecule of DNA, which of the following combinations of base pairs will be found?

D) A + C = G + T

Which of the following facts did Hershey and Chase make use of in trying to determine whether DNA or protein is the genetic material?

D) DNA contains phosphorus, whereas protein does not.

Which of the following statements correctly describes the difference between the leading strand and the lagging strand in DNA replication?

D) The leading strand is synthesized continuously in the 5' → 3' direction, while the lagging strand is synthesized discontinuously in the 5' → 3' direction.

The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage? A) telomerase, helicase, single-strand binding protein B) telomerase, primase, DNA polymerase C) DNA ligase, replication fork proteins, adenylyl cyclase D) nuclease, DNA polymerase, DNA ligase

D) nuclease, DNA polymerase, DNA ligase

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

DNA polymerase can join new nucleotides only to the 3′ end of a pre-existing strand, and the strands are antiparallel.

The lagging strand is characterized by a series of short segments of DNA (Okazaki fragments) that will be joined together to form a finished lagging strand. The experiments that led to the discovery of Okazaki fragments gave evidence for which of the following ideas?

DNA polymerase is an enzyme that synthesizes leading and lagging strands during replication only in one direction.