Question

Mendel blended his knowledge of science and mathematics to keep count of the individuals exhibiting a particular trait in each generation. He observed a number of contrasting visible characters controlled in pea plants in a field. He conducted many experiments to arrive at the laws of inheritance.

1. What do the F₁ progeny of tall plants with round seeds and short plants with wrinkled seeds look like?
2. Name the recessive traits in the above case.
3. Mention the type of the new combinations of plants obtained in F₂ progeny along with their ratio, if F₁ progeny was allowed to self-pollinate.

OR

If 1600 plants were obtained in F₂ progeny, write the number of plants having traits:

1. Tall with round seeds.
2. Short with wrinkled seeds.

Write the conclusion of the above experiment. 

Answer 1

(a) As tall and round are the dominant features, the F₁ offspring of tall plants with round seeds and short plants with wrinkled seeds will be heterozygous tall plants with round seeds (TtRr).

(b) The recessive traits are short plants and wrinkled seeds.

(c) The different types of combination obtained in F₂ progeny are:

F₁ progeny -

	TR	tR	Tr	tr
TR	TTRR Tall Round	TtRR Tall Round	TTRr Tall Round	TtRr Tall Round
tR	TtRR Tall Round	ttRR short round	TtRr Tall Round	ttRr Short round
Tr	TTRr Tall Round	TtRr Tall Round	TTrr Tall wrinkled	Ttrr Tall wrinkled
tr	TtRr Tall Round	ttRr Short round	Ttrr Short wrinkled	ttrr Tall wrinkled

Tall plants with round seeds = 9

Short plants with round seeds = 3

Tall plants with wrinkled seeds = 3

Short plants with wrinkled seeds = 1

Phenotypic ratio

= Tall round : short round : tall wrinkled : short wrinkled

= 9 : 3 : 3 : 1

OR

If 1600 plants were obtained in F₂ progeny, the number of plants having traits will be:

Tall plants with round seeds = `9/16 xx 1600` = 900

Short plants with wrinkled seeds `= 1/16 xx 1600` = 100

The conclusion of the above experiment states the "Law of independent assortment". This law states that the alleles of two (or more) different genes get sorted into gametes independently of one another.