In diploid species (2n), each individual inherits two gene variants (alleles) for each gene, one from the father and one from the mother. This means that each haploid gamete (n) receives one copy of each homologous chromosome that contains only one form of that gene (i.e., one allele). In consequence, and according to Mendel's First Law, alleles segregate into separate gametes (in this case either "A" allele or "a" allele since the parental genotype is heterozygous for this gene).
