Question 1

Which of the following is NOT one of the four essential characteristics that a molecule must exhibit to serve as genetic material?

Accepted Answer

It must be able to catalyze metabolic reactions.

Question 2

In the early 20th century, why did most scientists believe proteins, rather than DNA, were the genetic material?

Accepted Answer

Proteins are more chemically diverse than DNA.

Question 3

Which experimental result from Frederick Griffith’s work with Streptococcus pneumoniae demonstrated the principle of transformation?

Accepted Answer

Mice injected with a mixture of heat-killed virulent and live avirulent bacteria died, and live virulent bacteria could be recovered.

Question 4

Avery, MacLeod, and McCarty demonstrated that DNA is the transforming principle by showing that transformation did NOT occur when extracts were treated with which enzyme?

Accepted Answer

DNase

Question 5

In the Hershey-Chase experiment, which isotope was used to label DNA, and why was this significant?

Accepted Answer

$$^{32}\mathrm{P}$$, because phosphorus is present in DNA but not in protein.

Question 6

Which of the following best describes the central dogma of molecular biology?

Accepted Answer

DNA is transcribed into RNA, which is translated into protein.

Question 7

Which of the following provides indirect evidence that DNA is the genetic material in eukaryotes?

Accepted Answer

The amount of DNA in haploid cells is half that in diploid cells.

Question 8

Why is UV light at 260 nm particularly effective at causing mutations in DNA?

Accepted Answer

DNA absorbs UV light most strongly at 260 nm, leading to mutagenic effects.

Question 9

Which of the following statements about the structure of DNA is correct?

Accepted Answer

DNA is a double helix composed of two antiparallel strands.

Question 10

A scientist treats a bacterial extract with protease, RNase, and DNase separately, then mixes each with avirulent bacteria. Only the DNase-treated extract fails to transform the bacteria. What conclusion can be drawn?

Accepted Answer

DNA is required for transformation.

Question 11

Which of the following is a real-world application of the principle of transformation discovered by Griffith?

Accepted Answer

Bacterial acquisition of antibiotic resistance genes from the environment.

Question 12

Which of the following best explains why DNA, and not protein, is the genetic material in most organisms?

Accepted Answer

DNA fulfills all four criteria for genetic material: replication, storage, expression, and variation.

Question 13

Which of the following is a direct experimental proof that DNA is the biomolecule responsible for heredity?

Accepted Answer

Avery, MacLeod, and McCarty’s demonstration that DNase destroys transforming activity.

Question 14

Which of the following statements about RNA is correct?

Accepted Answer

RNA can serve as the genetic material in some viruses.

Question 15

A mutation occurs in a gene that encodes a DNA repair enzyme. Which of the four essential characteristics of genetic material is most directly affected?

Accepted Answer

Allowing variation by mutation.

Question 16

Which of the following scenarios best illustrates the concept of information flow from genetic material to phenotype?

Accepted Answer

A mutation in DNA leads to a change in the amino acid sequence of a protein, resulting in a new phenotype.

Question 17

Which of the following best describes the outcome of the Hershey-Chase experiment?

Accepted Answer

Only DNA, not protein, entered the bacterial cells and directed viral reproduction.

Question 18

Which of the following is a plausible reason why DNA, rather than RNA, is the primary genetic material in most organisms?

Accepted Answer

DNA is more chemically stable than RNA.

Question 19

Which of the following best explains why the amount of DNA in haploid cells is half that in diploid cells?

Accepted Answer

Haploid cells contain one set of chromosomes, while diploid cells contain two sets.

Question 20

Which of the following is a correct statement about the absorption of UV light by biomolecules?

Accepted Answer

DNA absorbs UV light most strongly at 260 nm, while protein absorbs most strongly at 280 nm.

DNA Structure and Analysis: The Discovery of DNA as the Genetic Material

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