Question

Compare the phenotypic variation seen in Mendelian inheritance, incomplete dominance, codominance, epistasis, and polygenic inheritance.

Answer 1

• Mendelian inheritance - The pattern by which genes and traits are passed from parents to their children. According to it, a dominant allele masks or the expression of a recessive allele and a recessive allele is an allele that exerts its effect only in the homozygous state and in heterozygous state its expression is masked by a dominant allele.
• Incomplete dominance or partial dominance or semidominance is a condition when neither allele is dominant over the other. This produces a heterozygote expressing an intermediate phenotype Showing same geotypic and phenotypic ratio of 1:2:1.
• Epistasis is the process where one gene masks or inhibits the expression another gene at distinct locus. It can be dominant epistasis where the dominant allele of one gene masks the effects of either allele of the second gene. This shows phenotypic ratio 12:3:1. Recessive epistasis - In this, one non allelic pair produces its phenotype independently in a dominant state but cannot produce a phenotype independently, showing phenotypic ratio 9:3:4
• Codominance - In this, alleles lack dominant and recessive feature and produces phenotypically same offspring. The heterpzygous genotype give rise to a phenotype distinctly different from either of the homozygous genotype.
• Polygenic inheritance - Quantitative traits are governed by many genes that each make a small contribution to the overall outcome. This inheritance pattern is sometimes called polygenic inheritance. In this, no allelic pairs exhibit dominance and there is no genetic interaction between alleles of different loci and no linkage between the loci.