Question

Duration: 3:00:00 Time Left : 2:31:25
When dihybrid TtRr take part in selfing, then what
is the probability of gametes having (T) allele
(A) 100%
(B) 50%
(C) 25%
(D) 75%​

Answer 1

Answer:-

Dihybrid plant with genotype TtRr when 5akes part in selfing, it means the genes of both the parent is TtRr.

If the gametes of this is separated, it will be obviously be: TR, Tr, tR and tr.

The Question asks, what will be the probability of gametes having allele as T.

So, the answer will be 2 out of 4.

In other words, from the options given, (B) 50%.

$\rule{200}2$

For extra knowledge:-

Now, Finding the progeny using the punnet square.

$\boxed{\begin{tabular}{c|c|c|c|c}\bf{-} & \bf{TR} & \bf{Tr} & \bf{tR} & \bf{tr} \\\cline{1-5}\bf{TR} & TTRR & TTRr & TtRR & TtRr\\\cline{1-5}\bf{Tr} & TTRr & TTrr & TtRr & Ttrr \\\cline{1-5}\bf{tR} & TtRR & TtRr & ttRR & trRr \\\cline{1-5}\bf{tr} & TtRr & Ttrr & ttRr & ttrr\end{tabular}}$

So, Phenotypic ratio:-

Tall and round = 9

Tall and wrinkled = 3

Short and round = 3

short and wrinkled = 1

So, ratio = 9:3:3:1

And, genotypic ratio:-

TTRR = 1

TTRr = 2

TTrr = 1

TtRR = 2

TtRr = 4

Ttrr = 2

ttRR = 1

ttRr = 2

ttrr = 1

So, ratio = 1:2:1:2:4:2:1:2:1

$\rule{200}2$