Which statement best defines a genetic mutation?

Which statement best defines a genetic mutation?

• A. A permanent change in the appearance of an animal
• B. A permanent change in the DNA sequence of a gene
• C. Differences between fraternal twins
• D. The suppression of a gene by chemical factors

Answer: (B)

A genetic mutation is a permanent change in the DNA sequence of a gene. This can be a small change, like a single nucleotide substitution, or a larger one, such as insertions, deletions, or rearrangements that alter the gene’s coding region or regulatory elements. Because it involves the sequence of DNA itself, it can affect the amino acid sequence of a protein or how a gene is expressed. If a mutation occurs in germ cells, it can be inherited by offspring; if it occurs in somatic cells, it affects only the individual. This definition is the best fit because mutations are about lasting changes to the genetic material, not just outward appearances, normal genetic variation between individuals (such as differences seen in fraternal twins), or changes in gene activity that occur without altering the DNA sequence (gene suppression by chemical factors).

A genetic mutation is a permanent change in the DNA sequence of a gene. This can be a small change, like a single nucleotide substitution, or a larger one, such as insertions, deletions, or rearrangements that alter the gene’s coding region or regulatory elements. Because it involves the sequence of DNA itself, it can affect the amino acid sequence of a protein or how a gene is expressed. If a mutation occurs in germ cells, it can be inherited by offspring; if it occurs in somatic cells, it affects only the individual.

This definition is the best fit because mutations are about lasting changes to the genetic material, not just outward appearances, normal genetic variation between individuals (such as differences seen in fraternal twins), or changes in gene activity that occur without altering the DNA sequence (gene suppression by chemical factors).