Both the homozygote phenotype so gets expressed in a heterozygote since it has both the alleles. It is a general explanation of codominance. However, incomplete dominance results in the expression of only one allele out of the two in a heterozygote. Hence, a homozygote consists of two doses of the gene product. Here we talk about haplosufficiency. Heterozygote showing normal dominance requires only half of the homozygous allele for expression of the phenotype. Dominance occurs due to the presence of a non-functional allele. Meaning, one allele loses its functions such as expressing a protein product or skips the process of transcription. It also occurs due to mutation altering the DNA sequence. Hence, the organism having a non-functional allele will show a particular phenotype. Example, albinism is an autosomal recessive disorder occurring due to the inefficient synthesis of the pigment melanin in the skin and the hair. Hence, such individuals show whitish-pink skin coloration. Let us consider the interaction between the alleles that make an allele recessive. The single allele produces a product or a phenotype identical to that of the homozygote (haplosufficiency). Hence, the functional allele becomes dominant to the non-functional one. In the case of an albino gene locus, the heterozygous individuals produce sufficient melanin in the skin. Hence, they exhibit normal pigmentation in the skin.