The phenotypic expression of a heterozygote in Mendelian inheritance shows
In Mendelian inheritance with complete dominance, heterozygote carries one dominant and one recessive allele but produces sufficient dominant gene product to achieve dominant phenotype threshold, such as enzyme activity or structural protein. Consequently phenotypic expression of heterozygote shows dominant trait, identical to homozygous dominant, e.g., tall Tt same as TT. Recessive trait appears only in tt lacking dominant allele. Blended or intermediate trait characterises incomplete dominance, not Mendelian complete dominance where heterozygote fully expresses dominant phenotype. Cytologica
Ref: Snustad & Simmons, Principles of Genetics, 7th ed., Chapter 3: Heterozygote Expression
