The shape of summer squash is classified as either long, spherical, or disk-shaped. Disk-shaped fruits are produced when dominant alleles are present at two gene loci, A and B. Spherical-shaped fruits are produced when a dominant allele is present at either the A or B gene loci. Long-shaped fruits are produced when the plant is homozygous recessive for both genes A and B. When a plant that produces spherical-shaped fruits is crossed with a plant that produces long-shaped fruits, the phenotypic proportion of the progeny obtained is as follows: 1/2 spherical fruit and 1/2 long fruit. Based on the segregation data, determine the genotype of the parents.