Question 1

Which experiment provided the first direct evidence that DNA is the genetic material responsible for transformation in bacteria?

Accepted Answer

Griffith's experiment with Streptococcus pneumoniae

Question 2

In the Hershey-Chase experiment, which radioactive isotope was used to label DNA, and what was the key finding?

Accepted Answer

$$^{32}\mathrm{P}$$; DNA entered the bacterial cell

Question 3

Chargaff’s rules state that in any DNA molecule:

Accepted Answer

The amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine

Question 4

Which of the following best describes the antiparallel structure of DNA?

Accepted Answer

One strand runs 5' to 3', and the other runs 3' to 5'

Question 5

What is the significance of the semiconservative model of DNA replication?

Accepted Answer

Each daughter DNA molecule consists of one parental and one new strand

Question 6

Which enzyme is responsible for unwinding the DNA double helix during replication?

Accepted Answer

Helicase

Question 7

Why are Okazaki fragments formed during DNA replication?

Accepted Answer

Because the lagging strand is synthesized discontinuously away from the replication fork

Question 8

Which enzyme removes RNA primers and replaces them with DNA nucleotides during replication?

Accepted Answer

DNA polymerase I

Question 9

A mutation occurs during DNA replication. Which process is most likely to correct this error?

Accepted Answer

Mismatch repair

Question 10

What is the function of telomeres in eukaryotic chromosomes?

Accepted Answer

They prevent the loss of genes near the ends of chromosomes during replication

Question 11

Which of the following best explains why cancer cells often have active telomerase?

Accepted Answer

To allow unlimited cell division by maintaining telomere length

Question 12

Which of the following is NOT a function of histone proteins?

Accepted Answer

Facilitating the supercoiling of DNA in prokaryotes

Question 13

A scientist observes that after several rounds of DNA replication in a eukaryotic cell, the chromosomes become progressively shorter. What is the most likely explanation?

Accepted Answer

DNA polymerase cannot complete the 5' ends of linear DNA

Question 14

Which of the following statements about euchromatin and heterochromatin is correct?

Accepted Answer

Euchromatin is loosely packed and generally accessible for transcription

Question 15

Which of the following best describes the role of topoisomerase during DNA replication?

Accepted Answer

It relieves overwinding strain ahead of the replication fork

Question 16

If a DNA sample contains 30% adenine, what percentage of guanine would you expect to find?

Accepted Answer

20%

Question 17

Which of the following is a direct consequence of the double helix structure of DNA for its replication?

Accepted Answer

Each strand can serve as a template for the synthesis of a new complementary strand

Question 18

Which enzyme is responsible for joining Okazaki fragments on the lagging strand during DNA replication?

Accepted Answer

DNA ligase

Question 19

A mutation in the gene encoding single-strand binding protein would most likely result in which of the following?

Accepted Answer

Single-stranded DNA re-annealing before replication can occur

Question 20

Which of the following best explains why DNA polymerase requires a primer to begin synthesis?

Accepted Answer

It can only add nucleotides to an existing 3' hydroxyl group

The Molecular Basis of Inheritance: DNA Structure, Replication, and Chromosome Organization

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