Question 1

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

Accepted Answer

A nucleotide contains a nitrogenous base, a pentose sugar, and a phosphate group, while a nucleoside contains only a nitrogenous base and a pentose sugar.

Question 2

Which bond is responsible for linking nucleotides together in the backbone of DNA and RNA?

Accepted Answer

Phosphodiester bond

Question 3

Which of the following statements about the directionality of nucleic acids is correct?

Accepted Answer

Nucleic acids are synthesized and read from the 5' to 3' direction.

Question 4

Which of the following best explains why DNA is more stable than RNA under physiological conditions?

Accepted Answer

DNA lacks a 2'-hydroxyl group on its sugar, making it less prone to hydrolysis.

Question 5

Which of the following base pairs is stabilized by three hydrogen bonds in double-stranded DNA?

Accepted Answer

Guanine–Cytosine

Question 6

What is the main function of the high-energy phosphoanhydride bonds in ATP?

Accepted Answer

To store and transfer energy for cellular processes

Question 7

Which of the following modifications is commonly found in eukaryotic DNA and plays a key role in epigenetic gene regulation?

Accepted Answer

5-methylcytidine

Question 8

During DNA denaturation, which bonds are broken and which remain intact?

Accepted Answer

Hydrogen bonds are broken; phosphodiester bonds remain intact.

Question 9

Which of the following is a function of tRNA in the cell?

Accepted Answer

Bringing amino acids to the ribosome during translation

Question 10

Which enzyme catalyzes the conversion of ATP to cAMP in response to hormonal signals?

Accepted Answer

Adenylyl cyclase

Question 11

A researcher is designing a PCR experiment. Why are primers necessary for DNA polymerase to function in vitro?

Accepted Answer

Primers provide a free 3'-OH group for DNA polymerase to extend the new strand.

Question 12

Which of the following best describes the role of base stacking interactions in the DNA double helix?

Accepted Answer

They provide additional stability through van der Waals and hydrophobic forces.

Question 13

Which of the following is true regarding the anti conformation of the N-glycosidic bond in nucleotides?

Accepted Answer

It is the most common conformation in DNA and RNA, allowing proper base pairing.

Question 14

Which of the following statements about mRNA processing in eukaryotes is correct?

Accepted Answer

The 5' end is capped with 7-methylguanylate, and the 3' end is polyadenylated.

Question 15

Which of the following best explains why GC-rich regions of DNA have a higher melting temperature ($$T_m) $$than AT-rich regions?

Accepted Answer

GC pairs form three hydrogen bonds, while AT pairs form two.

Question 16

Which of the following is a common secondary structure found in RNA molecules that is important for their function?

Accepted Answer

Hairpin loop

Question 17

Which of the following is a correct abbreviation for deoxyguanosine triphosphate?

Accepted Answer

dGTP

Question 18

Which of the following is a function of ribosomal RNA (rRNA)?

Accepted Answer

Catalyzing peptide bond formation during translation

Question 19

Which of the following best describes the process of DNA sequencing using dideoxynucleotide triphosphates (ddNTPs)?

Accepted Answer

ddNTPs terminate DNA synthesis at specific bases, allowing sequence determination by fragment length.

Question 20

Which of the following is a palindromic DNA sequence?

Accepted Answer

5'-GAATTC-3'

Nucleotides and Nucleic Acids: Structure, Function, and Biological Roles

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