16.2.4—Genes, proteins and phenotype

A gene can affect phenotype by encoding a protein or functional RNA. The protein may act as an enzyme, receptor, transporter or structural component; its activity changes a pathway that contributes to the phenotype.

A DNA change can alter expression, amino-acid sequence, folding or protein amount. The final phenotype depends on cell context, other genes and environmental conditions, not just the allele label.

A mutation in an enzyme gene can reduce pigment production, but temperature or nutrient supply may still modify how much pigment is visible.

One gene does not always map to one simple trait. Explain the molecular link before claiming a direct genotype–phenotype equivalence.