Question

Two heterozygous purple-flowering pea plants are crossed. If purple is dominant over white, what are the expected phenotypic results? A). 100% purple B). 75% purple, 25% white C). 50% purple, 50% white D). 25% purple, 75% white

Answer 1

Pp><Pp
= PP (purple homozygous)
2Pp (purple heterozygous)
pp (white)

purple= 3/4 . 100%
=75%
white=1/4 . 100%
= 25%

answer: b

Answer 2

The correct answer would be B). 75% purple, 25% white.

In Mendelian genetics, the cross between two heterozygous parents results in the production of offspring with a genotypic ratio of 1:2:1. They have a phenotypic ratio of 3 (dominant) : 1 (recessive).

The same can be explained with the help of Punnett square. Let us assume P (dominant) and p (recessive) be the alleles of the gene responsible for the color of flowers in a plant.

The genotype of parents would be Pp.

The cross would produce offspring with three possible genotype combinations which are PP, Pp, and pp in 1:2:1.

Plant with PP and Pp genotype will produce purple flowers and plant with pp genotype will produce white flowers.

Thus, 75% (3 out of 4) would purple-flowered plants and 25% (1 out of 4) would be a white-flowered plant.