There are two types of alleles. An allele that masks another is the homozygousphenotypeallelerecessiveheterozygousdominantX genotype allele. The one that is masked is called the homozygousphenotypeallelerecessiveheterozygousX dominantgenotype allele.An organism that has the same alleles for a particular trait is homozygousphenotypeallelerecessiveheterozygousdominantX genotype. An organism that has different alleles for a particular trait is X homozygousphenotypeallelerecessiveheterozygousdominantgenotype.