Question 1

Which interaction is the primary source of stability in the DNA double helix?

Accepted Answer

Base stacking interactions

Question 2

What is the main reason that DNA with a high G+C content is more stable than DNA with a high A+T content?

Accepted Answer

Stacking energies between G and C bases are greater than those between A and T bases

Question 3

Which form do double-helical regions of RNA most commonly adopt?

Accepted Answer

A-form

Question 4

During heat denaturation of DNA, which thermodynamic term becomes dominant at high temperature, favoring strand separation?

Accepted Answer

$$\Delta S_{conformational}$$

Question 5

Which equation correctly describes the free energy change for the double helix to random coil transition?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 6

Which of the following is NOT a role played by RNA in the cell?

Accepted Answer

Template for DNA replication

Question 7

A palindromic DNA sequence is important for which biological process?

Accepted Answer

Recognition by restriction endonucleases

Question 8

Which experimental technique relies on the ability of nucleic acids to hybridize by base pairing?

Accepted Answer

Polymerase Chain Reaction (PCR)

Question 9

Why does the absorbance of DNA bases at 260 nm increase upon denaturation?

Accepted Answer

Bases are less stacked and more exposed in the random coil state

Question 10

Which of the following statements about mRNA is TRUE?

Accepted Answer

mRNA tends to be single-stranded to be easily read by the ribosome

Question 11

Which of the following best describes the role of tRNA in protein synthesis?

Accepted Answer

tRNA serves as an adaptor that binds amino acids and matches them to mRNA codons

Question 12

Which of the following is a consequence of disrupting base stacking interactions in DNA?

Accepted Answer

Exposure of hydrophobic surfaces and destabilization of the helix

Question 13

Which type of RNA is the catalytic component of the ribosome?

Accepted Answer

rRNA

Question 14

Molnupiravir is a nucleoside mimic that induces mutations in SARS-CoV-2 by:

Accepted Answer

Mimicking cytidine and base pairing with either G or A

Question 15

Which of the following is a secondary structure commonly found in single-stranded RNA?

Accepted Answer

Hairpin loop

Question 16

What is the biological significance of DNA cruciform structures?

Accepted Answer

They facilitate the binding of proteins to specific DNA sequences

Question 17

Which antibiotic blocks the exit tunnel of the ribosome, inhibiting protein synthesis?

Accepted Answer

Erythromycin

Question 18

Which of the following best explains why high temperature denatures DNA?

Accepted Answer

High temperature increases $$T\Delta S$$, making $$\Delta G$$ negative and favoring strand separation

Question 19

Which of the following is TRUE about RNA secondary and tertiary structures?

Accepted Answer

RNA can form complex tertiary structures and act as a ribozyme

Question 20

Which process is monitored by measuring absorbance at 260 nm in nucleic acids?

Accepted Answer

Denaturation and renaturation of nucleic acids

Nucleic Acid Structure II: DNA and RNA Structure, Stability, and Function

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