What is mutation?

• A. The process of converting mRNA into a protein.
• B. A protein that helps with DNA replication.
• C. A DNA sequence that codes for tRNA.
• D. A change in the nucleotide sequence of DNA; the ultimate source of genetic diversity.

Answer: (D)

Mutation is a change in the nucleotide sequence of DNA, and it provides the raw material for genetic variation in a population. This variation is essential for evolution because natural selection and other forces act on new alleles that arise from mutations. Mutations can occur spontaneously during DNA replication or be caused by mutagens, and their effects can range from no change (due to the redundancy of the genetic code) to altered amino acids, to premature stop codons, or to changes in gene regulation. The other descriptions refer to different processes or molecules: translating mRNA into a protein is protein synthesis, a protein that helps with DNA replication is a replication enzyme, and a DNA sequence that codes for tRNA is a gene for tRNA.