A mutation that affects the number or structure of whole chromosomes is called a ______ mutation.

• A. Point mutation
• B. Gene regulation
• C. Chromosomal mutation
• D. Phenotype

Answer: (C)

Mutations that involve the number or structure of whole chromosomes are chromosomal mutations. This type changes what a chromosome looks like or how many copies exist, affecting many genes at once. Examples include having an extra chromosome, missing one, or rearrangements like deletions, duplications, inversions, or translocations of chromosome segments.

In contrast, a point mutation changes a single nucleotide within a gene, which is a much smaller-scale change and does not alter the overall chromosome number or big structure. Gene regulation refers to when genes are turned on or off, not to changes in chromosome structure. Phenotype describes the observable traits that result from genetics and environment, not a mutation type itself.