Dominant alleles express phenotype regardless of zygosity

Steps:

• Define dominant allele: expresses its phenotype even when paired with a recessive allele in heterozygotes.
• Evaluate A: mutations occur in all alleles, not excluded by dominance.
• Evaluate B: survival advantage depends on environment, not inherent to dominance.
• Evaluate C: matches definition, as phenotype appears in both Aa and AA genotypes.
• Evaluate D: allele frequencies vary by selection and drift, not dominance status.

Why C is correct:

• By definition, dominant alleles fully express their phenotype in heterozygotes (masking recessive) and homozygotes, yielding the same observable trait per Mendel's laws of inheritance.

Why the others are wrong:

• A: All alleles, dominant or recessive, can mutate under genetic principles.
• B: Dominance concerns phenotype expression, not guaranteed survival or fitness benefits.
• D: Recessive alleles can persist at higher frequencies in populations if masked in heterozygotes.

Final answer: C