Q: If a DNA molecule has the sequence 5'-ATCGGCTA-3', what is the complementary sequence?

$$3'\text{-}TAGCCGAT\text{-}5'$$

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 is studying a newly discovered organism and finds that its DNA contains 30% adenine. According to Chargaff’s rules, what percentage of guanine should be present?

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 in eukaryotic cells, why are multiple origins of replication necessary?

Accepted Answer

Eukaryotic chromosomes are much larger and linear, requiring multiple starting points to replicate efficiently.

Question 6

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

Accepted Answer

It joins Okazaki fragments on the lagging strand by forming phosphodiester bonds.

Question 7

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 8

Why do eukaryotic chromosomes have telomeres at their ends?

Accepted Answer

To protect genes from being eroded during successive rounds of DNA replication.

Question 9

Which enzyme is responsible for synthesizing short RNA primers during DNA replication?

Accepted Answer

Primase

Question 10

A mutation in the gene encoding DNA polymerase results in a loss of proofreading ability. What is the most likely consequence?

Accepted Answer

An increased rate of mutations in the newly synthesized DNA.

Question 11

Which of the following statements about the directionality of DNA synthesis is correct?

Accepted Answer

DNA polymerase adds nucleotides only to the 3' end of a growing DNA strand.

Question 12

Cancer cells often show inappropriate activity of which enzyme, contributing to their 'immortalization'?

Accepted Answer

Telomerase

Question 13

Which of the following best describes the composition of a nucleotide in DNA?

Accepted Answer

A nitrogenous base, a deoxyribose sugar, and a phosphate group

Question 14

If a DNA molecule has the sequence 5'-ATCGGCTA-3', what is the complementary sequence?

Accepted Answer

$$3'	ext{-}TAGCCGAT	ext{-}5'$$

Question 15

Which of the following is a direct result of the antiparallel structure of DNA during replication?

Accepted Answer

The lagging strand is synthesized in short fragments away from the replication fork.

Question 16

A researcher observes that after several rounds of cell division, the chromosomes in a cell line are significantly shorter. Which enzyme is most likely deficient in these cells?

Accepted Answer

Telomerase

Question 17

Which of the following best explains why Okazaki fragments are formed during DNA replication?

Accepted Answer

DNA polymerase can only synthesize DNA in the 5' to 3' direction, so the lagging strand is synthesized discontinuously.

Question 18

Which of the following is NOT a function of DNA polymerase during DNA replication?

Accepted Answer

Unwinding the DNA double helix

Question 19

A mutation causes the loss of single-strand binding proteins during DNA replication. What is the most likely immediate effect?

Accepted Answer

The separated DNA strands would re-anneal, preventing replication.

Question 20

Which of the following equations correctly represents the dehydration synthesis reaction catalyzed by DNA polymerase during DNA strand elongation?

Accepted Answer

$$	ext{(DNA)}_n + 	ext{dNTP} ightarrow 	ext{(DNA)}_{n+1} + 	ext{PP}_i$$

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

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