When one gene affects multiple traits, we call this pleiotropy . If multiple genes affect the trait, the genotype consists of all loci that affect that trait. Genotypes Note that two organisms with the same phenotype may have different genotypes. This can be due to Dominance and gene interaction. Dominance refers to the ability of the phenotype of one allele to mask the phenotype of another allele.
Recessive alleles are alleles that can be masked by a dominant allele.
In this case there is a different phenotype for each genotype. Codominance A and a are codominant if the products of both alleles can be detected in the Aa heterozygotes. At the protein level, many alleles are codominant. At the DNA sequence level, all alleles are codominant if they differ at the sequence level, since both can be detected. Alleles of genes on different chromosomes are passed on independently of one another.