Question 1

Which of the following best describes the structure of a nucleotide, the monomer of nucleic acids?

Accepted Answer

A sugar, a phosphate group, and a nitrogen-containing base

Question 2

What is the key structural difference between ribonucleotides and deoxyribonucleotides?

Accepted Answer

Ribonucleotides have a hydroxyl group at the 2' carbon of the sugar, while deoxyribonucleotides have a hydrogen at the same position.

Question 3

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

Accepted Answer

Nucleic acid sequences are always written from the 5' to 3' direction.

Question 4

Which of the following best explains why the addition of phosphate groups to a nucleotide raises its potential energy?

Accepted Answer

Phosphate groups are negatively charged and their repulsion stores potential energy, which can be released during condensation reactions.

Question 5

During the formation of a phosphodiester bond between two nucleotides, which molecule is released as a byproduct?

Accepted Answer

$$\mathrm{H_2O}$$

Question 6

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

Accepted Answer

Uracil

Question 7

According to Chargaff's rules, which of the following equations is correct for double-stranded DNA?

Accepted Answer

$$[A] = [T]$$ and $$[G] = [C]$$

Question 8

Which of the following best describes the backbone of RNA?

Accepted Answer

A sugar-phosphate backbone with ribose sugars

Question 9

Which of the following statements about the double helix structure of DNA is correct?

Accepted Answer

The two strands are held together by hydrogen bonds between complementary nitrogenous bases.

Question 10

Which of the following is a unique property of RNA compared to DNA?

Accepted Answer

RNA can catalyze chemical reactions as well as carry sequence information.

Question 11

Which of the following best explains why only purine-pyrimidine pairs fit inside the DNA double helix?

Accepted Answer

Purine-pyrimidine pairs have just the right size to fit within the helix, while purine-purine pairs are too large and pyrimidine-pyrimidine pairs are too small.

Question 12

Which of the following best describes the antiparallel nature of DNA?

Accepted Answer

The two strands run in opposite directions: one 5' to 3', the other 3' to 5'.

Question 13

Which scientist(s) are credited with building the first accurate model of the DNA double helix?

Accepted Answer

James Watson and Francis Crick

Question 14

Which of the following best describes the role of Rosalind Franklin in the discovery of DNA structure?

Accepted Answer

She provided critical X-ray diffraction data that helped reveal the double helical structure.

Question 15

A scientist is synthesizing a new strand of DNA. Which of the following is required for the condensation reaction that forms the phosphodiester bond?

Accepted Answer

A nucleotide triphosphate as a substrate

Question 16

Which of the following best explains why the condensation reaction that forms nucleic acid polymers is not energetically favorable on its own?

Accepted Answer

It requires the input of energy, which is provided by the hydrolysis of nucleotide triphosphates.

Question 17

Which of the following base pairs is held together by three hydrogen bonds in DNA?

Accepted Answer

Guanine and Cytosine

Question 18

Which of the following is a correct statement about the function of nucleic acids?

Accepted Answer

They store and transmit genetic information.

Question 19

Which of the following is a real-world example of RNA's catalytic activity?

Accepted Answer

The ribosome's peptidyl transferase activity during protein synthesis

Question 20

A mutation causes a DNA strand to have two purines paired together. What is the most likely structural consequence?

Accepted Answer

The double helix will be distorted because purine-purine pairs are too large to fit properly.

Nucleic Acids and the RNA World: Structure, Function, and Key Discoveries

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