Question 1

Which of the following best describes the main finding of the Hershey-Chase experiment?

Accepted Answer

DNA is the genetic material responsible for heredity in bacteriophages.

Question 2

According to Chargaff’s rules, if a double-stranded DNA molecule contains 30% adenine, what percentage of guanine does it contain?

Accepted Answer

$$20\%$$

Question 3

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

Accepted Answer

The sugar-phosphate backbone is held together by hydrogen bonds.

Question 4

A scientist isolates a nucleic acid with the following base composition: $$A = 24.0\%$$, $$G = 23.3\%$$, $$C = 21.4\%$$, $$T = 31.3\%. $$What is the most likely nature of this nucleic acid?

Accepted Answer

It is a single-stranded DNA molecule.

Question 5

Which analytical technique is most appropriate for separating DNA fragments by size?

Accepted Answer

Electrophoresis

Question 6

If the base sequence of one DNA strand is $$5'	ext{-}ATGCCGTA-3'$$, what is the sequence of the complementary strand?

Accepted Answer

$$3'	ext{-}TACGGCAT-5'$$

Question 7

Which of the following is NOT a characteristic that genetic material must exhibit?

Accepted Answer

Ability to catalyze metabolic reactions

Question 8

In the Meselson-Stahl experiment, what result would you expect after two rounds of replication if DNA replication were conservative?

Accepted Answer

One old, heavy band and one new, light band

Question 9

Which of the following best explains why DNA is more stable than RNA for long-term storage of genetic information?

Accepted Answer

DNA lacks a 2' hydroxyl group on the sugar, making it less susceptible to hydrolysis.

Question 10

A DNA sample is heated from $$30^\circ C to$$ $$100^\circ C$$ while measuring absorbance at $$260 nm. $$What is the expected result?

Accepted Answer

Absorbance increases sharply at the melting temperature due to denaturation (hyperchromic shift).

Question 11

Which of the following statements about the Watson and Crick model of DNA is correct?

Accepted Answer

The helix is right-handed and has major and minor grooves.

Question 12

Which enzyme treatment in the Avery, MacLeod, and McCarty experiment destroyed the transforming principle?

Accepted Answer

DNase

Question 13

Which of the following is NOT consistent with Chargaff’s findings?

Accepted Answer

$$(C + G) = (A + T)$$

Question 14

Which of the following best describes the difference between a nucleoside and a nucleotide?

Accepted Answer

A nucleotide contains a phosphate group, while a nucleoside does not.

Question 15

Which of the following would be the outcome of the Hershey-Chase experiment if protein (and not DNA) was the carrier of genetic information?

Accepted Answer

The infected bacteria would be positive for $$^{35}S$$ radioactive labeling, and not $$^{32}P.$$

Question 16

Which of the following is a real-world application of molecular hybridization?

Accepted Answer

Detecting specific DNA sequences in chromosomes using FISH

Question 17

Which of the following equations would you use to calculate the melting temperature ($$T_m) of a $$DNA sequence with 12 nucleotides, where $$w is $$the number of A, $$x is $$the number of T, $$y is $$the number of G, and $$z is $$the number of C?

Accepted Answer

$$T_m = (wA + xT) * 2 + (yG + zC) * 4$$

Question 18

Which of the following statements about Okazaki fragments is correct?

Accepted Answer

They are short DNA fragments synthesized on the lagging strand during replication.

Question 19

Which of the following is a key difference between B-DNA and Z-DNA?

Accepted Answer

B-DNA is right-handed, while Z-DNA is left-handed.

DNA Structure and Replication: Foundations of Genetic Material

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