Question

question 4 of 10
which sentence describes a mutation that occurs as a result of exposure to
ionizing radiation?
a. compounds insert themselves into dnas double helix.
b. uv light causes chemical bonds to form between cytosines.
c. an incorrect nucleotide is added during dna replication.
d. a new genetic combination results from crossing over.

Explanation:

UV light is a form of ionizing radiation. When DNA is exposed to UV light, it can cause adjacent cytosine bases in the DNA strand to form chemical bonds with each other (pyrimidine dimers). This is a type of mutation caused by ionizing radiation.

• Option A: Compounds inserting into DNA's double helix is more related to chemical mutagens (like intercalating agents) rather than ionizing radiation effects.
• Option C: An incorrect nucleotide added during DNA replication is often due to errors in the normal DNA replication machinery (like DNA polymerase mistakes) rather than ionizing radiation - induced mutations.
• Option D: A new genetic combination from crossing over is a normal process in meiosis (genetic recombination) and not a mutation caused by ionizing radiation.

Answer:

B. UV light causes chemical bonds to form between cytosines.