Question 1

Which experiment provided the most definitive evidence that DNA is the hereditary material in cells?

Accepted Answer

The Hershey-Chase experiment using bacteriophages and radioactive labeling

Question 2

What type of bond connects the 3' carbon of one deoxyribose to the 5' phosphate of the next in the DNA backbone?

Accepted Answer

Phosphodiester bond

Question 3

During DNA replication, which enzyme is responsible for unwinding the double helix by breaking hydrogen bonds between bases?

Accepted Answer

Helicase

Question 4

A patient with xeroderma pigmentosum (XP) is highly sensitive to sunlight. What is the underlying molecular defect in XP?

Accepted Answer

Defective nucleotide excision repair enzymes

Question 5

Which of the following best describes the directionality of DNA synthesis?

Accepted Answer

DNA is synthesized in the 5' to 3' direction

Question 6

A point mutation changes a single base pair from GC to AT in a gene. Which disease is a classic example of a point mutation causing a major phenotype?

Accepted Answer

Sickle-cell anemia

Question 7

Which enzyme synthesizes a short stretch of RNA to provide a free 3' OH group for DNA polymerase during replication?

Accepted Answer

Primase

Question 8

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

Accepted Answer

They prevent separated DNA strands from re-annealing

Question 9

Which process allows bacteria to acquire genetic material from their environment, such as DNA fragments released by dead cells?

Accepted Answer

Transformation

Question 10

UV light can cause adjacent thymine bases in DNA to form covalent bonds, resulting in a kink. What is the name of this type of DNA damage?

Accepted Answer

Thymine dimer

Question 11

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

Accepted Answer

DNA ligase

Question 12

In the Meselson-Stahl experiment, what was the key evidence supporting the semiconservative model of DNA replication?

Accepted Answer

After one round of replication, DNA molecules had intermediate density

Question 13

Which of the following is NOT a mechanism by which bacteria exchange genetic material?

Accepted Answer

Binary fission

Question 14

A mutation that deletes or inserts a single nucleotide in a coding region of DNA is most likely to cause which type of mutation?

Accepted Answer

Frameshift mutation

Question 15

Which enzyme relieves the twisting and supercoiling tension ahead of the replication fork during DNA replication?

Accepted Answer

Topoisomerase

Question 16

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

Accepted Answer

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

Question 17

Which formula correctly represents the base pairing in DNA?

Accepted Answer

$$A = T$$ and $$G = C$$

Question 18

If a DNA molecule has 30% adenine, what percentage of guanine does it contain?

Accepted Answer

20%

Question 19

Which process involves the transfer of genetic material between bacteria via a pilus?

Accepted Answer

Conjugation

Question 20

A scientist exposes bacteria to nitrous acid, which increases the rate of base substitution mutations. What type of mutation is most likely to result?

Accepted Answer

Point mutation

DNA and Gene: Synthesis and Repair – Study Notes

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