Q: Which of the following best explains why bases in nucleic acids are hydrophobic despite containing nitrogen atoms?

The planar, pseudoaromatic ring structure allows for $$c$$ electron stacking, making the bases hydrophobic.

Question 1

Which of the following correctly distinguishes a nucleoside from a nucleotide?

Accepted Answer

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

Question 2

Which of the following statements about purines and pyrimidines is CORRECT?

Accepted Answer

Purines have two rings and nine constituent atoms, while pyrimidines have one ring and six constituent atoms.

Question 3

Which of the following best explains why DNA polymerase has a lower mutation rate than HIV reverse transcriptase?

Accepted Answer

DNA polymerase has proofreading activity, while HIV reverse transcriptase lacks proofreading.

Question 4

Which of the following is the correct net charge of a nucleotide triphosphate (NTP) at pH 7?

Accepted Answer

$$-4$$

Question 5

A mutation occurs when a base is in a rare tautomeric form during DNA replication. According to Watson and Crick, what is the most likely consequence of this event?

Accepted Answer

The base may pair incorrectly, leading to a point mutation in the newly synthesized DNA strand.

Question 6

Which of the following best describes the difference between ribose and deoxyribose sugars in nucleic acids?

Accepted Answer

Ribose has a hydroxyl group at the 2' carbon, while deoxyribose has a hydrogen at the 2' carbon.

Question 7

Which of the following bonds connects the base to the sugar in a nucleotide?

Accepted Answer

Glycosidic bond

Question 8

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

Accepted Answer

Uracil

Question 9

At physiological pH ($$pH = 7$$), what is the expected charge on the phosphate group of a nucleotide?

Accepted Answer

$$-1$$

Question 10

Which of the following best describes the structure of ATP?

Accepted Answer

Adenosine (adenine + ribose) attached to three phosphate groups via phosphoanhydride bonds

Question 11

Which of the following is a correct one-letter and three-letter code pair for a DNA nucleobase?

Accepted Answer

A, Ade

Question 12

Which of the following statements about the phosphoanhydride bond in nucleotides is TRUE?

Accepted Answer

It is a high-energy bond found between phosphate groups in ATP.

Question 13

A patient with untreated AIDS produces approximately $$10^{10}$$ virus particles per day. If the mutation rate is 1 mutation per 10,000 bases and the viral genome is 9,500 bases, how many new mutations are expected per day?

Accepted Answer

$$1 	imes 10^9$

Question 14

Which of the following modifications distinguishes thymine from uracil?

Accepted Answer

Thymine has a methyl group at the C5 position, while uracil does not.

Question 15

Which of the following best explains why bases in nucleic acids are hydrophobic despite containing nitrogen atoms?

Accepted Answer

The planar, pseudoaromatic ring structure allows for $$c$$ electron stacking, making the bases hydrophobic.

Question 16

Which of the following is the correct order of components in a nucleotide from 5' to 3'?

Accepted Answer

Phosphate - Sugar - Base

Question 17

Which of the following best describes the effect of pH on the ionization state of the phosphate group in nucleotides?

Accepted Answer

At pH 7, the phosphate group is deprotonated and carries a negative charge.

Question 18

Which of the following is a correct description of the difference between a nucleotide monophosphate, diphosphate, and triphosphate?

Accepted Answer

A monophosphate has one phosphate group, a diphosphate has two, and a triphosphate has three phosphate groups attached to the sugar.

Question 19

Which of the following best explains why the addition of phosphate groups increases the solubility of nucleotides in water?

Accepted Answer

Phosphate groups are highly charged and hydrophilic, increasing the overall solubility of the molecule.

Question 20

Which of the following is the correct name for the nucleotide with the base guanine, a ribose sugar, and three phosphate groups?

Accepted Answer

Guanosine 5'-triphosphate (GTP)

Nucleic Acids: Structure, Components, and Mutation Mechanisms

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