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AP Biology Practice Quiz: Nucleic Acids

Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026

Test your understanding with short quizzes. This quiz has 11 questions to check your progress.

Question 1 of 11

According to the provided text, what are the three fundamental components of a single nucleotide monomer?

All Questions (11)

According to the provided text, what are the three fundamental components of a single nucleotide monomer?

A) A five-carbon sugar, a phosphate group, and a nitrogenous base

B) A double helix, a hydroxyl group, and a phosphate group

C) A ribose sugar, a deoxyribose sugar, and a nitrogenous base

D) An amino acid, a phosphate group, and a 3' end

Correct Answer: A

The content explicitly states, 'Each nucleotide contains a five-carbon sugar, a phosphate group, and a nitrogenous base.'

During the synthesis of a nucleic acid polymer, where are new nucleotides incorporated into the growing chain?

A) At the 5' phosphate end

B) At the 3' hydroxyl end

C) To the nitrogenous base of the previous nucleotide

D) Randomly along the sugar-phosphate backbone

Correct Answer: B

The text specifies that 'During synthesis, new nucleotides are added to the 3' end,' which is the 3' hydroxyl end.

A segment of a DNA double helix is found to contain 30% adenine (A). What percentage of the segment is composed of guanine (G)?

A) 20%

B) 30%

C) 40%

D) 70%

Correct Answer: A

Based on the specific base pairing rules for DNA (A-T and C-G), if adenine is 30%, then thymine must also be 30%. This accounts for 60% of the bases. The remaining 40% must be cytosine and guanine. Since they pair together, they must be in equal amounts, so guanine makes up half of the remaining 40%, which is 20%.

Which of the following describes a key structural difference between DNA and RNA?

A) DNA contains a phosphate group, while RNA does not.

B) DNA is typically single-stranded, while RNA is typically double-stranded.

C) DNA contains the sugar deoxyribose, while RNA contains the sugar ribose.

D) DNA uses adenine as a nitrogenous base, while RNA uses guanine.

Correct Answer: C

The content lists three key structural differences, one of which is 'the type of sugar (deoxyribose vs. ribose).'

In an RNA molecule, which nitrogenous base forms a pair with adenine (A)?

A) Thymine (T)

B) Cytosine (C)

C) Guanine (G)

D) Uracil (U)

Correct Answer: D

The text states, 'In RNA, adenine pairs with uracil (A-U).' This is a key distinction from DNA, where adenine pairs with thymine.

The structure of DNA is described as an 'antiparallel double helix.' What does the term 'antiparallel' refer to?

A) The two strands have identical base sequences but run in the same direction.

B) The two strands have complementary base sequences and run in opposite 5' to 3' directions.

C) The helix twists to the left in one direction and to the right in the other.

D) The sugar-phosphate backbones are on the inside of the helix, and the bases are on the outside.

Correct Answer: B

The text establishes that nucleic acids have 'defined 3' hydroxyl and 5' phosphate ends' and that DNA is a 'double helix.' The term 'antiparallel' describes how these two strands are oriented relative to each other, with one strand running 5' to 3' and the other running 3' to 5'.

What is the primary function of nucleic acids as described in the provided information?

A) To provide structural support to the cell wall.

B) To catalyze metabolic reactions as enzymes.

C) To encode biological information.

D) To act as a short-term energy storage molecule.

Correct Answer: C

The content directly states that 'Nucleic acids encode biological information in sequences of nucleotide monomers.'

A scientist isolates a nucleic acid and determines that it is single-stranded and contains the nitrogenous base uracil. Which conclusion is most strongly supported by this evidence?

A) The molecule is DNA.

B) The molecule is RNA.

C) The molecule is a hybrid of DNA and RNA.

D) The molecule is a protein.

Correct Answer: B

The content identifies two key features of RNA that distinguish it from DNA: it contains uracil instead of thymine, and it is typically single-stranded. Both observations point to the molecule being RNA.

If one strand of a DNA molecule has the sequence 5'-AGTC-3', what is the sequence of the complementary strand?

A) 5'-TCAG-3'

B) 3'-UCAG-5'

C) 5'-GACT-3'

D) 3'-TCAG-5'

Correct Answer: D

Based on base pairing rules, A pairs with T, and G pairs with C. Therefore, the complementary sequence to AGTC is TCAG. Because DNA is an antiparallel double helix, the complementary strand must run in the opposite direction, so the correct sequence is 3'-TCAG-5'.

A new nucleotide is being added to a growing DNA strand. The phosphate group of the incoming nucleotide will form a bond with which part of the existing strand?

A) The phosphate group at the 5' end

B) The nitrogenous base of the last nucleotide

C) The hydroxyl group at the 3' end

D) The deoxyribose sugar of the first nucleotide

Correct Answer: C

The content states that nucleic acids have a 'defined 3' hydroxyl and 5' phosphate ends' and that 'new nucleotides are added to the 3' end.' This addition occurs when the phosphate of the new nucleotide bonds to the 3' hydroxyl group of the last nucleotide in the chain.

Which pair correctly matches the nucleic acid with its typical strandedness and one of its unique nitrogenous bases?

A) DNA: single-stranded, Uracil

B) RNA: double-stranded, Thymine

C) DNA: double-stranded, Thymine

D) RNA: single-stranded, Guanine

Correct Answer: C

The content specifies that DNA is 'typically double-stranded' and contains thymine, while RNA is 'typically single-stranded' and contains uracil. Option C correctly identifies the characteristics of DNA.