Genes are segments of DNA that are the basic unit of heredity. They are passed on from parent to offspring. The gene form of a trait is called a(n) homozygousphenotype✔ allelerecessiveheterozygousdominantX genotype.An organism’s allele combination is called the homozygousX phenotypeallelerecessiveheterozygousdominant✔ genotype.The physical appearance of an organism is called the homozygous✔ phenotypeallelerecessiveheterozygousdominantgenotype.