Question 1

Which scientist's X-ray crystallography images were crucial in deducing the helical structure of DNA?

Accepted Answer

Rosalind Franklin

Question 2

Why does pairing a purine with a pyrimidine in DNA result in a uniform width of the double helix?

Accepted Answer

Because the combined size of a purine and a pyrimidine matches the spacing required for the double helix

Question 3

A woman’s paternal grandfather had hemophilia. What is the probability that she is a carrier?

Accepted Answer

$\frac{1}{2}$

Question 4

Which feature of DNA allows it to be replicated in a semi-conservative manner?

Accepted Answer

Its double helix structure with complementary base pairing

Question 5

During DNA replication, why is the lagging strand synthesized in fragments?

Accepted Answer

Because DNA polymerase can only synthesize DNA in the 5' to 3' direction, but the lagging strand template runs 3' to 5'

Question 6

Which equation correctly represents Chargaff’s rule for base pairing in DNA?

Accepted Answer

$[A] = [T]$ and $[G] = [C]$

Question 7

Species A has 4 million GC pairs and 2 million AT pairs. Species B has 4 million AT pairs and 2 million GC pairs. Which species is likely to survive at higher temperatures and why?

Accepted Answer

Species A, because GC pairs form three hydrogen bonds, making the DNA more stable at high temperatures

Question 8

What is the function of telomeres in eukaryotic chromosomes?

Accepted Answer

They postpone the erosion of genes near the ends of chromosomes

Question 9

Which enzyme is responsible for lengthening telomeres in germ cells?

Accepted Answer

Telomerase

Question 10

Why is DNA replication described as 'antiparallel elongation'?

Accepted Answer

Because the two DNA strands run in opposite directions and DNA polymerase can only add nucleotides to the free 3' end

Question 11

What is the evolutionary significance of mutations in DNA?

Accepted Answer

They are a source of genetic variation upon which natural selection operates

Question 12

Which process repairs DNA by removing and replacing damaged stretches?

Accepted Answer

Nucleotide excision repair

Question 13

If the error rate after proofreading and repair is $1 	imes 10^{-10}$ per base pair, how many errors would you expect in a human genome of $3 	imes 10^{9}$ base pairs after one round of replication?

Accepted Answer

$3 	imes 10^{-1}$

Question 14

Which statement best describes the difference between bacterial and eukaryotic chromosomes?

Accepted Answer

Bacterial chromosomes are double-stranded, circular DNA molecules with small amounts of protein, while eukaryotic chromosomes are linear DNA molecules with large amounts of protein

Question 15

What is the consequence of repeated rounds of DNA replication in eukaryotic cells without telomerase activity?

Accepted Answer

Essential genes may be lost from the ends of chromosomes

Question 16

Which of the following best explains why telomerase activity is often found in cancer cells?

Accepted Answer

It allows cancer cells to maintain their telomeres and divide indefinitely

Question 17

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

Accepted Answer

Initiating DNA strand synthesis by laying down RNA primers

Question 18

Which real-world scenario best illustrates the importance of DNA repair mechanisms?

Accepted Answer

A person exposed to UV radiation develops skin cancer due to unrepaired DNA damage

Question 19

Which of the following best describes chromatin packing in eukaryotic chromosomes?

Accepted Answer

Chromosomes fit into the nucleus through an elaborate, multilevel system of packing

Question 20

Which direction does DNA polymerase synthesize new DNA strands?

Accepted Answer

5' to 3'

Molecular Basis of Inheritance: DNA Structure, Replication, and Chromosomal Organization

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