Question

A snapdragon plant homozygous for red flower when crossed with a white flowered plant of the same species produced pink flowers in F₁ generation. 

(a) What is this phenotypic expression called? 

(b) Work out the cross to show the F₂ generation when F₁ was self-pollinated. Give the phenotypic and genotypic ratios of F₂ generation. 

(c) How do you compare the F₂ phenotypic and genotypic ratios with those of Mendelian monohybrid F₂ ratios?

Answer 1

(a) This phenotype expression is called incomplete dominance.

(c) The phenotypic ratio deviates from a typical Mendelian monohybrid ratio of 3 : 1 to 1 : 2 : 1. Since the heterozygous hybrid individual shows a different phenotype, i.e., pink colour flowers. The genotypic ratio remains the same as the Mendelian monohybrid ratio, which is also 1 : 2 : 1.