$$8 \times 2 + 6 \times 3 = 34$$ hydrogen bonds

Question 1

Which of the following statements correctly describes a difference between DNA and RNA with respect to their sugar components?

Accepted Answer

DNA contains deoxyribose, while RNA contains ribose.

Question 2

A DNA fragment contains 8 A-T pairs and 6 G-C pairs. How many total hydrogen bonds are present in this fragment?

Accepted Answer

$$8 	imes 2 + 6 	imes 3 = 34$$ hydrogen bonds

Question 3

Which base pair is considered a 'wobble' base pair in RNA, and what is its biological significance?

Accepted Answer

G-U; enables flexibility in codon-anticodon pairing during translation

Question 4

What is the typical diameter of the DNA double helix?

Accepted Answer

$$\approx 2.0 nm$$

Question 5

Which of the following correctly describes the directionality of nucleic acid synthesis during replication and transcription?

Accepted Answer

Synthesis occurs in the 5' to 3' direction.

Question 6

A student is asked to label the sugar carbons in a nucleotide. Which carbon is attached to the phosphate group?

Accepted Answer

5' carbon

Question 7

Which of the following base pairs is stabilized by three hydrogen bonds?

Accepted Answer

G-C in DNA

Question 8

If a DNA strand has the sequence 5'-G C A T T C G A-3', what is the complementary strand (with correct directionality)?

Accepted Answer

3'-C G T A A G C T-5'

Question 9

Which of the following statements best explains why RNA is more chemically labile at high pH than DNA?

Accepted Answer

RNA has a 2'-OH group on the ribose sugar, which can participate in base-catalyzed hydrolysis.

Question 10

Which of the following is a purine base found in both DNA and RNA?

Accepted Answer

Adenine

Question 11

What is the function of nucleosomes in eukaryotic cells?

Accepted Answer

They compact DNA by wrapping it around histone proteins, forming higher-order chromatin structures.

Question 12

Which of the following would increase the melting temperature ($$T_m) of a $$DNA fragment?

Accepted Answer

Increasing the number of G-C base pairs

Question 13

A researcher isolates RNA and DNA from a cell. Which of the following conditions would selectively degrade RNA but not DNA?

Accepted Answer

Incubation in basic (alkaline) conditions

Question 14

Which of the following is true regarding the anti-parallel arrangement of DNA strands?

Accepted Answer

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

Question 15

Which of the following is a consequence of cytosine deamination in DNA?

Accepted Answer

Conversion of cytosine to uracil, potentially leading to mutation if unrepaired

Question 16

Which of the following best describes the role of ribozymes?

Accepted Answer

They are RNA molecules that possess catalytic activity.

Question 17

A DNA molecule is found to have 30% adenine. What is the expected percentage of guanine in this molecule?

Accepted Answer

20%

Question 18

Which of the following is NOT a pyrimidine base?

Accepted Answer

Adenine

Question 19

Which of the following best explains why GC-rich DNA fragments have higher melting temperatures than AT-rich fragments?

Accepted Answer

GC pairs form three hydrogen bonds, requiring more energy to separate.

Question 20

Which of the following is the correct order of nucleic acid backbone atoms from 5' to 3' direction?

Accepted Answer

Phosphate - 5' carbon - 3' carbon

Nucleic Acids: Structure, Base Pairing, and Biochemical Principles

Study Guide - Practice Questions