Question 1

Which of the following best explains why DNA replication is described as 'semiconservative'?

Accepted Answer

Each daughter DNA molecule consists of one parental strand and one newly synthesized strand.

Question 2

Rosalind Franklin's X-ray crystallography images were critical in determining which feature of DNA structure?

Accepted Answer

That DNA is helical and has a uniform width with sugar-phosphate backbones on the outside.

Question 3

A scientist observes that the percentage of adenine in a DNA sample is 30%. According to Chargaff’s rules, what is the expected percentage of guanine in this sample?

Accepted Answer

$$20\%$$

Question 4

Which enzyme is responsible for relieving the strain caused by the unwinding of the DNA double helix during replication?

Accepted Answer

Topoisomerase

Question 5

During DNA replication, why is an RNA primer necessary for DNA polymerase to begin synthesis?

Accepted Answer

DNA polymerase can only add nucleotides to an existing 3' end.

Question 6

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

Accepted Answer

The leading strand is synthesized continuously toward the replication fork, while the lagging strand is synthesized discontinuously away from the fork in Okazaki fragments.

Question 7

A mutation causes the loss of function of DNA ligase in a cell. Which of the following would most likely result?

Accepted Answer

Okazaki fragments on the lagging strand would not be joined together.

Question 8

Which of the following is a direct consequence of the inability of DNA polymerase to replicate the very ends of linear chromosomes?

Accepted Answer

Progressive shortening of chromosomes with each cell division.

Question 9

Telomerase is active in which of the following cell types, and what is its primary function?

Accepted Answer

Germ cells; it extends telomeres to prevent loss of genetic information.

Question 10

A patient is exposed to high levels of UV radiation, resulting in thymine dimers in their DNA. Which DNA repair mechanism is most likely to correct this damage?

Accepted Answer

Nucleotide excision repair

Question 11

Which of the following statements about DNA polymerase is FALSE?

Accepted Answer

It can initiate synthesis of a new DNA strand without a primer.

Question 12

If a eukaryotic cell lacked single-strand binding proteins during DNA replication, what would most likely occur?

Accepted Answer

The separated DNA strands would re-anneal before replication could proceed.

Question 13

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

Accepted Answer

It relieves the strain caused by overwinding ahead of the replication fork.

Question 14

A mutation in a gene encoding a DNA repair enzyme leads to an increased rate of cancer in affected individuals. Which of the following best explains this observation?

Accepted Answer

Failure to repair DNA damage increases the likelihood of mutations that can lead to uncontrolled cell division.

Question 15

Which of the following equations correctly represents the relationship between the percentages of nitrogenous bases in double-stranded DNA according to Chargaff’s rules?

Accepted Answer

$$\%A = \%T$$ and $$\%G = \%C$$

Question 16

Which of the following is a real-world consequence of telomere shortening in human somatic cells?

Accepted Answer

It is associated with cellular aging and limits the number of times a cell can divide.

Question 17

Which enzyme is responsible for removing RNA primers and replacing them with DNA nucleotides during lagging strand synthesis?

Accepted Answer

A specific DNA polymerase

Question 18

In prokaryotic DNA replication, how many origins of replication are typically present, and what is the result?

Accepted Answer

One origin of replication, resulting in two replication forks moving in opposite directions.

Question 19

A cancer cell line is found to have high telomerase activity. What is the most likely consequence of this observation?

Accepted Answer

The cancer cells can divide indefinitely without losing essential genetic information.

Question 20

Which of the following best describes the chemical reaction catalyzed by DNA polymerase during DNA synthesis?

Accepted Answer

Formation of a phosphodiester bond through a dehydration synthesis reaction.

Molecular Basis of Inheritance: DNA Structure, Replication, and Repair

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