Genotype

The two alleles an organism has for a characteristic are its genotype. The characteristic that develops is part of its phenotype. The link is not simply that a letter ‘becomes’ a visible feature: alleles are versions of DNA instructions, and their effects on proteins help produce the phenotype.

The combination of alleles an organism has for a gene is its genotype. The characteristic produced is part of its phenotype. A phenotype results from the effects of the allele pair together; each allele does not give the organism a separate whole-organism phenotype.

An organism's genotype is the combination of alleles it has for its genes. When studying one gene, the genotype means the pair of alleles carried for that gene. More broadly, an organism's genotype includes its allele combinations across its genes.