Question

In summer squash, gene pair Q causes development of white colour and it is dominant over colour development (q). At another locus, gene pair G causes development of yellow colour, and is dominant to green (g) colour. The genes interact in such a way that dominant white (Q) hides, the effects of either G or g on the phenotype.

What is the phenotypic ratio that will be expected if the following two genotypes are crossed? QqGg and Qqgg. Just indicate the ratio

Answer 1

Answer:

In summer squash, three types of fruit colours appear, white, yellow and green. White colour is controlled by dominant gene W and yellow colour by dominant gene G. White is dominant over both yellow and green. The green fruits are produced in recessive condition (wwgg). A cross between plants having white and yellow fruits produced F1 with white fruits. Inter-mating of F1 plants produced plants with white, yellow and green coloured fruits in F2 in 12 : 3 : 1 ratio. Here W is dominant to w and epistatic to alleles G and g. Hence it will mask the expression of G/g alleles. Hence in F2, plants with W-G-(9/16) and Wwgg (3/16) genotypes will produce white fruits; plants with wwG-(3/16) will produce yellow fruits and those with wwgg (1/16) genotype will produce green fruits.