Question

(a) A garden pea plant bearing terminal, violet flowers when crossed with another pea plant bearing axial, violet flowers, produced axial, violet flower and axial, white flowers in the ratio of $3:1$. Work out the cross showing the genotypes of the parent pea plants and their progeny.
(b) Name and state the law that can be derived from this cross and not from a monohybrid cross.

Answer 1

Parents: ttpp x TtPp

Gametes: tP, tp TP, Tp, tP, tp

	tp	tp
TP	TtPP Axial, purple flowers	TtPp Axial, purple flowers
Tp	TtPp Axial, purple flowers	Ttpp Axial, white flowers
tP	ttPP terminal purple flowers	ttPp terminal, purple flowers
tp	ttPp Terminal purple flowers	ttpp Terminal white flowers

In pea plants, violet flowers are dominant over white flowers and axial position of flowers is dominant over terminal position. It is given that, a garden pea plant bearing terminal, violet flowers is crossed with another pea plant bearing axial, violet flowers. This produced axial, violet flowers and axial, white flowers in the ratio of 3:1.
Since, both axial, violet and axial, white flowers are produced, then the genotype of the parents can only be ttPp (terminal, violet flowers) and TtPp (axial, violet flowers).

(b) The above cross is governed by the law of independent assortment. According to this law, when two pairs of traits are combined in a hybrid, one pair of character segregates independent of the other pair of character"