What is the difference between genotype and phenotype?

• A. Genotype is the set of alleles present; phenotype is the observable traits resulting from genotype and environment.
• B. Genotype refers to external appearance; phenotype refers to genes.
• C. Genotype changes with environment; phenotype remains constant.
• D. Genotype and phenotype are the same thing.

Answer: (A)

Genotype is the genetic blueprint—the set of alleles an organism carries. It remains largely fixed for an individual and determines the potential traits that could be expressed. Phenotype is what we actually observe—the visible or measurable traits that result from how those alleles are expressed in the body, influenced by environmental factors. This distinction explains why the same genotype can lead to different appearances under different conditions, and why environmental context matters for the final traits.

The best description says genotype is the set of alleles and phenotype are the observable traits arising from genotype and environment. The other statements confuse these concepts: external appearance is phenotype, not genotype; genotype generally doesn’t change with the environment (except rare mutations); and genotype and phenotype are not the same thing.