Question 1

Which of the following best describes the difference between a nucleoside and a nucleotide?

Accepted Answer

A nucleoside contains a nitrogenous base and a sugar, while a nucleotide contains a nitrogenous base, a sugar, and one or more phosphate groups.

Question 2

Which property of the triphosphate group in nucleotides is most responsible for its ability to drive unfavorable biochemical reactions?

Accepted Answer

Its high free energy of hydrolysis, making the breakdown of phosphoanhydride bonds highly exergonic.

Question 3

Which of the following correctly pairs a purine with its complementary pyrimidine in DNA according to Watson-Crick base pairing?

Accepted Answer

Adenine pairs with thymine.

Question 4

What is the main structural difference between DNA and RNA that contributes to the greater stability of DNA?

Accepted Answer

DNA contains a 2'-deoxyribose sugar, which lacks a hydroxyl group at the 2' position, making it less susceptible to hydrolysis.

Question 5

Which of the following best describes the directionality of nucleic acid synthesis?

Accepted Answer

Nucleic acids are synthesized in the 5' to 3' direction, with new nucleotides added to the 3' hydroxyl group.

Question 6

A researcher is analyzing the melting temperature ($$T_m) of $$two DNA samples. Sample A has 60% GC content, and Sample B has 40% GC content. Which sample will have the higher $$T_m$$, and why?

Accepted Answer

Sample A, because GC pairs form three hydrogen bonds, increasing thermal stability.

Question 7

Which of the following statements about phosphodiester bonds is correct?

Accepted Answer

Phosphodiester bonds form between the 3' hydroxyl of one nucleotide and the 5' phosphate of the next.

Question 8

During DNA replication, which enzyme is responsible for removing RNA primers and filling in the resulting gaps with DNA?

Accepted Answer

DNA polymerase I

Question 9

A DNA sequence is palindromic if:

Accepted Answer

It reads the same 5' to 3' on one strand and 5' to 3' on the complementary strand.

Question 10

Which of the following best explains the concept of semi-conservative replication?

Accepted Answer

Each new DNA molecule consists of one parental strand and one newly synthesized strand.

Question 11

Which of the following is a function of restriction endonucleases in molecular biology?

Accepted Answer

They digest DNA at specific sequences, producing defined fragments.

Question 12

A scientist uses a restriction enzyme that produces sticky ends. What is the main advantage of sticky ends in recombinant DNA technology?

Accepted Answer

Sticky ends facilitate the specific and efficient joining of complementary DNA fragments.

Question 13

Which of the following best describes the process of denaturation in DNA?

Accepted Answer

The separation of double-stranded DNA into single strands due to the breaking of hydrogen bonds.

Question 14

Which of the following is NOT a difference between B-form and A-form DNA?

Accepted Answer

B-form DNA has a right-handed helix, while A-form DNA is left-handed.

Question 15

Which enzyme is responsible for catalyzing the formation of phosphodiester bonds during DNA replication?

Accepted Answer

DNA polymerase

Question 16

Which of the following best describes the role of tRNA in translation?

Accepted Answer

tRNA brings amino acids to the ribosome by matching its anticodon to the mRNA codon.

Question 17

A DNA sample is subjected to increasing temperature, and the fraction of double-stranded DNA is measured. The resulting curve is sigmoidal. What does the midpoint of this curve represent?

Accepted Answer

The temperature at which 50% of the DNA is denatured (the melting temperature, $$T_m).$$

Question 18

Which of the following statements about the genetic code is correct?

Accepted Answer

The genetic code is universal, with most organisms using the same codon assignments.

Question 19

Which of the following best describes the function of a nuclease?

Accepted Answer

A nuclease hydrolyzes (digests) nucleic acids by cleaving phosphodiester bonds.

Question 20

During gene expression, what is the correct order of the main steps?

Accepted Answer

Transcription, then translation

Nucleic Acids: Structure, Properties, and Function Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards