Question

which sentence describes a mutation that occurs due to exposure to chemicals?
a. an incorrect nucleotide is spontaneously added during dna replication.
b. compounds insert themselves into dnas double helix.
c. a new genetic combination is produced by crossing over.
d. radiation causes bonds to form between cytosines.

Explanation:

• Option A: Spontaneous addition during DNA replication is not due to chemical exposure.
• Option B: Compounds (chemicals) inserting into DNA's double helix is a mutation caused by chemical exposure.
• Option C: Crossing - over is a normal genetic recombination process, not chemical - induced mutation.
• Option D: Radiation is a physical mutagen, not a chemical one.

Answer:

B. Compounds insert themselves into DNA's double helix.