Answer to Question #128771 in Evolution for Sinchan

Question

Give the genotypic and phenotypic ratio in the f2 generation in incomplete dominance.

Answer 1

Incomplete dominance is the condition when none of factors of a gene is dominant, the phenotype of heterozygous dominant individual is blend of dominant and recessive traits. For example flower colour in Antirrhinum majus shows incomplete dominance and the monohybrid cross between two pure varieties gives 1 : 2 : 1 phenotypic ratio in F2 generation which is 3 : 1 in otherwise dominant traits. The heterozygous genotypes in this case do not show the dominant trait but they are blend of dominant and recessive phenotype. A cross between two pure breeding genotypes that differ in two pairs of trait (dihybrid cross) followed by selfing of F1 hybrid gives 9 : 3 : 3 : 1 phenotypic ratio and 1 : 2 : 1 : 4 : 1 : 1 : 2 : 1 : 2 : 1 genotypic ratio.