Q: Which of the following equations correctly represents the dehydration synthesis (condensation) reaction that forms a phosphodiester bond between two nucleotides?

$$\text{Nucleotide}_1 + \text{Nucleotide}_2 \rightarrow \text{Dinucleotide} + H_2O$$

Question 1

Which of the following best describes the difference between a ribonucleotide and a deoxyribonucleotide?

Accepted Answer

A ribonucleotide has a hydroxyl group at the 2' carbon of its sugar, while a deoxyribonucleotide lacks this hydroxyl group.

Question 2

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

Accepted Answer

The 5' end of a nucleic acid strand has a free phosphate group, while the 3' end has a free hydroxyl group.

Question 3

Which scientist first provided evidence that DNA is helical in structure using X-ray crystallography?

Accepted Answer

Rosalind Franklin

Question 4

If a segment of DNA has the sequence 5'–ATCGGCTA–3', what is the sequence of its complementary strand?

Accepted Answer

3'–TAGCCGAT–5'

Question 5

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

Accepted Answer

DNA has a deoxyribose sugar, which lacks a hydroxyl group at the 2' carbon, making it less reactive.

Question 6

Which of the following is a function unique to RNA and not DNA?

Accepted Answer

Catalyzing chemical reactions as a ribozyme

Question 7

A mutation causes a cytosine (C) in DNA to be replaced by a thymine (T). Which of the following base-pairing changes would you expect in the double helix?

Accepted Answer

A G–C pair is replaced by an A–T pair.

Question 8

Which of the following best describes the process by which nucleotides are joined to form nucleic acids?

Accepted Answer

Condensation reactions form phosphodiester linkages between the 5' phosphate of one nucleotide and the 3' hydroxyl of another.

Question 9

Which of the following equations correctly represents the dehydration synthesis (condensation) reaction that forms a phosphodiester bond between two nucleotides?

Accepted Answer

$$	ext{Nucleotide}_1 + 	ext{Nucleotide}_2 ightarrow 	ext{Dinucleotide} + H_2O$$

Question 10

Which of the following is a correct statement about the secondary structure of DNA?

Accepted Answer

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

Question 11

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

Accepted Answer

Purine-purine pairs are too wide and pyrimidine-pyrimidine pairs are too narrow.

Question 12

Which of the following is a real-world application of the tertiary structure of DNA?

Accepted Answer

DNA's tertiary structure allows it to be compacted into chromatin, enabling efficient cell division.

Question 13

Which of the following best describes the secondary structure of RNA?

Accepted Answer

RNA forms hairpin loops due to complementary base pairing within the same strand.

Question 14

Which of the following is a property that makes RNA more versatile than DNA?

Accepted Answer

RNA can both store information and catalyze chemical reactions.

Question 15

A scientist is studying a molecule that contains ribose, uracil, and is capable of catalyzing a reaction. What is this molecule most likely to be?

Accepted Answer

A ribozyme

Question 16

Which of the following best explains why the sugar-phosphate backbone of DNA is hydrophilic?

Accepted Answer

The negatively charged phosphate groups face outward, interacting with water.

Question 17

Which of the following is a correct statement about complementary base pairing in DNA?

Accepted Answer

A pairs with T and C pairs with G.

Question 18

Which of the following best describes the role of hydrogen bonds in the structure of DNA?

Accepted Answer

Hydrogen bonds hold the two DNA strands together by connecting complementary bases.

Question 19

Which of the following is a plausible explanation for why RNA is less stable than DNA in cells?

Accepted Answer

RNA has a hydroxyl group at the 2' carbon, making it more susceptible to hydrolysis.

Nucleic Acids and the RNA World: Structure, Function, and Evolution

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