Question 1

Which of the following statements correctly describes the difference between DNA and RNA at the molecular level?

Accepted Answer

DNA contains the sugar deoxyribose and the base thymine, while RNA contains ribose and uracil.

Question 2

Which base pairing rule is followed in the Watson-Crick model of DNA?

Accepted Answer

A pairs with T via two hydrogen bonds, and G pairs with C via three hydrogen bonds.

Question 3

What is the primary structure of a nucleic acid?

Accepted Answer

The sequence of nucleotides connected by phosphodiester bonds.

Question 4

Which experiment provided definitive evidence for the semiconservative nature of DNA replication?

Accepted Answer

Meselson-Stahl's density gradient centrifugation experiment.

Question 5

What is the significance of the major and minor grooves in the DNA double helix?

Accepted Answer

They provide sites for protein and drug binding, affecting gene regulation.

Question 6

Which of the following best describes the antiparallel orientation of DNA strands?

Accepted Answer

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

Question 7

Which property of nucleotides allows for their detection and quantification using spectrophotometry?

Accepted Answer

Their absorption of ultraviolet light at around 260 nm.

Question 8

What is the role of phosphodiester linkages in nucleic acids?

Accepted Answer

They form the backbone by linking the 3'-hydroxyl of one nucleotide to the 5'-phosphate of the next.

Question 9

Why is RNA more susceptible to alkaline hydrolysis than DNA?

Accepted Answer

RNA has a 2'-hydroxyl group that can participate in nucleophilic attack, forming a cyclic intermediate.

Question 10

Which of the following is a tertiary structure of nucleic acids?

Accepted Answer

Supercoiling and cruciform structures.

Question 11

What is the biological function of telomeric G-quadruplexes?

Accepted Answer

They protect the ends of linear DNA molecules from degradation.

Question 12

Which of the following factors promotes the denaturation of double-stranded DNA?

Accepted Answer

Electrostatic repulsion between phosphate groups, high entropy, alkali, and heat.

Question 13

According to the central dogma of molecular biology, what is the correct flow of genetic information?

Accepted Answer

DNA → RNA → Protein

Question 14

Which enzyme is responsible for synthesizing RNA from a DNA template during transcription?

Accepted Answer

RNA polymerase

Question 15

A DNA sample has 30% adenine. According to Chargaff's rules, what percentage of guanine would you expect?

Accepted Answer

20%

Question 16

Which of the following best explains the outcome of the Meselson-Stahl experiment after one generation in light medium?

Accepted Answer

All DNA was intermediate in density, supporting the semiconservative model.

Question 17

Which of the following is NOT a tool or technique used to manipulate DNA?

Accepted Answer

Protein translation at the ribosome

Question 18

What is the effect of high ionic strength on the stability of the DNA double helix?

Accepted Answer

It stabilizes the duplex structure by neutralizing phosphate group charges.

Question 19

Which of the following statements about tautomerization in nucleic acid bases is correct?

Accepted Answer

Tautomerization is the reversible conversion between different structural forms, such as keto-enol and amino-imino.

Question 20

Which of the following best describes the structure of Z-DNA?

Accepted Answer

It is a left-handed helix with pyrimidines in anti and purines in syn orientation.

Nucleic Acids: Structure, Properties, and Biological Functions

Study Guide - Practice Questions