Today, we know these "factors" are alleles. an allele is an alternative form of a gene that is located at a specific position on a specific chromosome. we usually have two alleles for a trait, one inherited from each parent. we can rework mendel's original crosses with the notation for the alleles for seed color. this notation is called the genotype. when the pair of alleles is identical, they are called homozygous. when the pair is different, they are called heterozygous. capital letters represent dominant traits; lower case letters represent recessive traits. dominant traits can mask recessive traits. the colors yellow and green are called the phenotype. how would we describe the genotype of the green seeds?