Q: Which of the following reactions occurs during the formation of a phosphodiester bond in nucleic acid synthesis?

$$\text{NTP} + (DNA)_{n} \rightarrow (DNA)_{n+1} + PP_i$$

Question 1

Which of the following bases is found in RNA but not in DNA?

Accepted Answer

Uracil

Question 2

During the polymerization of nucleotides to form nucleic acids, which phosphate group forms the phosphodiester bond, and what is released as a byproduct?

Accepted Answer

The $$\alpha-$$phosphate forms the phosphodiester bond and the $$\beta$$ and $$\gamma$$ phosphates are released as pyrophosphate

Question 3

A molecule consisting of ribose linked by an N-glycosidic bond to N-9 of adenine is best described as:

Accepted Answer

Adenosine

Question 4

What structural difference distinguishes a ribonucleotide from a deoxyribonucleotide?

Accepted Answer

A deoxyribonucleotide has an —H instead of an —OH at C-2 of the ribose

Question 5

Which statement about double-stranded regions of RNA is correct?

Accepted Answer

They can form between two self-complementary regions of the same single strand of RNA

Question 6

The immediate energy source for DNA synthesis in cells is:

Accepted Answer

The exchange of a phosphoanhydride for a phosphate ester and the hydrolysis of pyrophosphate

Question 7

Which of the following is true regarding the pentoses found in nucleic acids?

Accepted Answer

The pentoses are always in the $$\beta-$$furanose forms

Question 8

Which class of nucleic acid is most abundant in all cells?

Accepted Answer

Ribosomal ribonucleic acid (rRNA)

Question 9

Why is ribonucleic acid (RNA) chemically less stable than deoxyribonucleic acid (DNA)?

Accepted Answer

The 2' hydroxyl group is positioned next to the phosphodiester bond and acid or base promotes an attack by the -OH group on the phosphate

Question 10

Depurination refers to:

Accepted Answer

The loss of adenine from DNA by the hydrolysis of the N-glycosidic bond between deoxyribose and the base

Question 11

A scientist is analyzing a nucleic acid sample and finds that it contains uracil, ribose, and forms double-stranded regions within a single molecule. Which type of nucleic acid is most likely present?

Accepted Answer

tRNA

Question 12

Which of the following best explains why DNA is more suitable than RNA for long-term storage of genetic information?

Accepted Answer

DNA lacks a 2' hydroxyl group, making it less susceptible to hydrolysis

Question 13

Which of the following reactions occurs during the formation of a phosphodiester bond in nucleic acid synthesis?

Accepted Answer

$$	ext{NTP} + (DNA)_{n} ightarrow (DNA)_{n+1} + PP_i$$

Question 14

A mutation causes the loss of the N-glycosidic bond between deoxyribose and a purine base in DNA. What is the most likely consequence?

Accepted Answer

Depurination

Question 15

Which of the following best describes the orientation of the two strands in a typical DNA double helix?

Accepted Answer

One strand runs 5' to 3', the other 3' to 5' (antiparallel)

Question 16

Which of the following is a direct result of the hydrolysis of pyrophosphate ($$PP_i) $$during DNA synthesis?

Accepted Answer

It provides energy to drive the polymerization reaction forward

Question 17

Which of the following statements about the bond between a nitrogenous base and a pentose sugar in nucleic acids is correct?

Accepted Answer

It is an N-glycosidic bond

Question 18

A patient is exposed to a chemical that promotes hydrolysis of the N-glycosidic bond in DNA. Which type of mutation is most likely to increase?

Accepted Answer

Depurination

Question 19

Which of the following best explains why the 2' hydroxyl group in RNA contributes to its instability?

Accepted Answer

It can attack the adjacent phosphodiester bond, leading to cleavage

Question 20

Which of the following is a correct description of adenosine?

Accepted Answer

Adenine linked to ribose via an N-glycosidic bond

Nucleic Acids: Structure, Function, and Chemistry – Guided Study

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