Question 1

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

Accepted Answer

The Hershey–Chase experiment

Question 2

What is the primary chemical difference between DNA and protein that allowed Hershey and Chase to distinguish between them using radioactive isotopes?

Accepted Answer

DNA contains phosphorus, while protein contains sulfur

Question 3

Which of the following best describes the structure of a DNA molecule?

Accepted Answer

A double-stranded helix with antiparallel strands

Question 4

What type of bond forms the backbone of a DNA strand?

Accepted Answer

Phosphodiester bond

Question 5

Which base pairs are correctly matched in DNA according to complementary base pairing?

Accepted Answer

Adenine–Thymine and Guanine–Cytosine

Question 6

During DNA replication, which enzyme is responsible for unwinding the double helix?

Accepted Answer

DNA helicase

Question 7

What is the function of single-strand DNA-binding proteins (SSBPs) during DNA replication?

Accepted Answer

They prevent separated DNA strands from re-annealing

Question 8

Which of the following statements about DNA polymerase is correct?

Accepted Answer

It can only add nucleotides to the 3′ end of a DNA strand

Question 9

Why is DNA replication considered semiconservative?

Accepted Answer

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

Question 10

What is the role of primase during DNA replication?

Accepted Answer

It synthesizes short RNA primers

Question 11

Okazaki fragments are formed during the synthesis of which DNA strand?

Accepted Answer

Lagging strand

Question 12

Which enzyme is responsible for joining Okazaki fragments together?

Accepted Answer

DNA ligase

Question 13

Why do linear chromosomes shorten with each round of DNA replication in most somatic cells?

Accepted Answer

DNA polymerase cannot replicate the very end of the lagging strand

Question 14

What is the function of telomerase?

Accepted Answer

It extends the 3′ end of the lagging strand using an RNA template

Question 15

Which of the following best explains why most cancer cells can divide indefinitely?

Accepted Answer

They have active telomerase

Question 16

Which DNA repair mechanism is responsible for correcting mismatched bases immediately after DNA synthesis?

Accepted Answer

Mismatch repair

Question 17

A patient with xeroderma pigmentosum (XP) is highly sensitive to sunlight. What is the underlying cause of this condition?

Accepted Answer

Defective nucleotide excision repair enzymes

Question 18

Which of the following is a direct consequence of unrepaired DNA damage in genes that control the cell cycle?

Accepted Answer

Uncontrolled cell division and possible tumor formation

Question 19

Which of the following equations correctly represents the directionality of DNA synthesis?

Accepted Answer

$$5' \rightarrow 3'$$

Question 20

A scientist exposes bacterial cells to UV light, causing thymine dimers to form. Which DNA repair system is most likely to fix this damage?

Accepted Answer

Nucleotide excision repair

DNA and the Gene: Synthesis and Repair – Study Notes

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