Question 1

Which experiment provided the first strong evidence that DNA, and not protein, is the genetic material in cells?

Accepted Answer

Hershey-Chase experiment with bacteriophage T2 and radioactive labeling

Question 2

What is the main structural difference between DNA and RNA nucleotides?

Accepted Answer

DNA contains deoxyribose and thymine, while RNA contains ribose and uracil

Question 3

According to Chargaff's rules, if a DNA sample contains 30% adenine, what percentage of guanine would you expect to find?

Accepted Answer

$$20\%$$

Question 4

Which of the following best describes the structure of the DNA double helix as proposed by Watson and Crick?

Accepted Answer

Two antiparallel strands with sugar-phosphate backbone on the outside and paired bases on the inside

Question 5

Which chemical bond links adjacent nucleotides in a single strand of DNA?

Accepted Answer

Phosphodiester bond

Question 6

In the Avery, MacLeod, and McCarty experiment, which enzyme treatment prevented transformation of R cells to S cells?

Accepted Answer

DNase

Question 7

What is the repeating unit (monomer) of nucleic acids such as DNA and RNA?

Accepted Answer

Nucleotide

Question 8

Which of the following statements about prokaryotic genomes is correct?

Accepted Answer

They are usually a single, circular chromosome with possible plasmids

Question 9

What is the function of topoisomerases in DNA structure?

Accepted Answer

They wind and unwind DNA to relieve supercoiling stress

Question 10

Which of the following is NOT a difference between DNA and RNA?

Accepted Answer

DNA contains uracil, RNA contains thymine

Question 11

A mutation changes a single base in a gene from G to A. Which of the following is the most direct molecular consequence?

Accepted Answer

A change in the DNA sequence, which may alter the RNA and protein

Question 12

Which of the following best explains why proteins were originally thought to be the genetic material instead of DNA?

Accepted Answer

Proteins are more chemically complex, with 20 amino acids compared to DNA's 4 bases

Question 13

Which of the following is a correct description of a nucleosome?

Accepted Answer

A segment of DNA wrapped around eight histone proteins

Question 14

If a DNA molecule is 3.4 nm long per turn and contains 10 base pairs per turn, what is the distance between adjacent base pairs?

Accepted Answer

$$0.34\ nm$$

Question 15

Which of the following is a real-world application of the discovery that DNA is the genetic material?

Accepted Answer

Gene therapy for inherited diseases

Question 16

Which of the following best describes the polarity of a DNA strand?

Accepted Answer

One end has a free 5' phosphate, the other has a free 3' hydroxyl group

Question 17

Which of the following statements about viral genomes is correct?

Accepted Answer

Viral genomes can be DNA or RNA, single- or double-stranded, circular or linear

Question 18

Which of the following is a direct result of the antiparallel orientation of DNA strands?

Accepted Answer

The 5' to 3' direction of one strand is opposite to the 3' to 5' direction of the other

Question 19

Which of the following best explains the significance of Rosalind Franklin's X-ray crystallography photo (Photo 51) in the discovery of DNA structure?

Accepted Answer

It provided evidence for the helical structure and regular repeating distances in DNA

DNA as the Genetic Material: Discovery, Structure, and Organization

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