question_answer

(i)  What are the characteristic feautures of a true-breeding line?

(ii) In peas, tallness is dominant over dwarfhess, and red colour of flowers is dominant over the white colour. When a tall plant bearing red flowers was pollinated by 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 types of four off springs.

 

Answer:

(i)  A true-breeding line for a trait is one that, has undergone continuous self-pollination or brother-sister mating, showing a stability in the inheritance of the trait for several generations.

(ii) 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 & Red \[\times \] Dwarf & White

(Tt Rr)                                (ttrr)

TR Tr               \[\times \]              tr

tR tr

 

	tr
TR	TrRr	Tall Red
Tr	Ttee	Tall White
tR	TtRr	Dwarf Red
tr	ttrr	Dwarf white