Question

In peas, tallness is dominant over dwarfness, and red colour of flowers is dominant over the white colour. When a tall plant bearing red flowers was pollinated with a dwarf plant bearing white flowers, the different phenotypic groups were obtained in the progeny in numbers mentioned against them:

Tall, Red = 138
Tall, White = 132
Dwarf, Red = 136
Dwarf, White = 128

Mention the genotypes of the two parents and of the four offspring types.

Answer 1

The result shows that the four types of offspring are in a ratio of 1:1:1:1. Such a result is observed in a test-cross progeny of a dihybrid cross.

The cross can be represented as:

Tall and Red (Tt Rr) × Dwarf and white (ttrr) 

off springs		tr
Tt Rr – Tall, Red  Tt rr – Tall, White Tt Rr – dwarf, red tt rr – dwarf, white	TR	TtRr	Tall	Red
	Tr	Ttrr	Tall	White
	tR	ttRr	dwarf	Red
	tr	ttrr	dwarf	white