Question

In a genetic experiment, plants with pure round green seeds (RRyy) were crossed with plants with wrinkled yellow seeds (rrYY).

1. Show the gametes formed when F₁ was self-pollinated.
2. A total of 144 seeds were produced which developed into saplings. Show the ratio in which these traits are independently inherited in these 144 sapling.

Answer 1

i. The parents of the F₁ generation were a pure round green seed plant (RRyy) and a pure wrinkled yellow seed plant (rrYY). The F₁ offspring would have the genotype RrYy.

When this F₁ plant is self-pollinated, it produces four types of gametes due to independent assortment:

RY, Ry, rY, ry

ii. A total of 144 seeds were produced, which developed into saplings
According to Mendel’s law of independent assortment, the F₂ generation shows a 9 : 3 : 3 : 1 phenotypic ratio. 9 round yellow, 3 round green 3 wrinkled yellow and 1 wrinkled green.

Out of 144 saplings, the number of each type will be:

Round yellow = `9/16 xx 144` = 81

Round green = `3/16 xx 144` = 27

Wrinkled Yellow = `3/16 xx 144` = 27

Wrinkled Green = `1/16 xx 144` = 9

Hence, the traits are inherited independently, and the saplings show the traits in the ratio 81 : 27 : 27 : 9, which matches the 9 : 3 : 3 : 1 pattern explained by Mendel.