A change in the DNA that can alter an organism's phenotype is called:

• A. Adaptation
• B. Polymorphism
• C. Phenocopy
• D. Mutation

Answer: (D)

A mutation is a permanent change in the DNA sequence that can alter the structure or regulation of a gene. This new DNA change can change the protein produced or how a gene is expressed, which in turn can lead to a different phenotype. This makes mutation the correct concept when a DNA change is linked to a phenotypic difference.

Other terms describe different ideas: adaptation is the process by which populations accumulate advantageous traits over generations; polymorphism refers to existing genetic variation within a population, not necessarily due to a new DNA change; a phenocopy is a phenotype caused by environmental factors that mimics a genetic trait, not a direct DNA alteration. For example, a single nucleotide change in a gene coding for hemoglobin can produce sickle-cell traits, illustrating how a DNA change can impact phenotype.