Question

1:1:1:1 genotypic ratio of progenies can be obtained if the plants being crossed have the genotypes
A. TTRR x ttRR
B. TtRr x ttrr
C. TtRR x ttrr
D. Ttrr x ttRr

• A. A, C, D
• B. A, B, C, D
• C. B, D
• D. A, B, C

Answer 1

The correct option is C B, D

1:1:1:1 ratio of progenies can be obtained if the plants for crossing are: TtRr x ttrr and Ttrr x ttRr.

For TtRr x ttrr, the gametes from TtRr would be
The gamete from ttrr would be of only one type - tr
Possible progenies genotypes can be obtained by using Punnett square
$\begin{array}{cc}\text{Gametes}& \text{tr}\\ \text{TR}& \text{TtRr}\\ \text{Tr}& \text{Ttrr}\\ \text{tR}& \text{ttRr}\\ \text{tr}& \text{ttrr}\end{array}$
Therefore, TtRr, Ttrr, ttRr, ttrr are found in the ratio of 1: 1: 1: 1
For Ttrr x ttRr,
Gametes produced from Ttrr : Tr, tr
Gametes produced from ttRr:
Possible progenies can be obtained by using Punnett square.
$\begin{array}{ccc}\text{Gametes}& \text{Tr}& \text{tr}\\ \text{tR}& \text{TtRr}& \text{ttRr}\\ \text{tr}& \text{Ttrr}& \text{ttrr}\end{array}$
Therefore, TtRr, ttRr, Ttrr, ttrr are found in the ratio of 1: 1: 1: 1
For TTRR x ttRR,
Gametes produced from TTRR would be of only one type- TR.
Gametes produced from ttRR would be of only one type- tR.
Therefore, all the progenies will be of TtRR genotype.

For TtRR x ttrr,
Gametes produced from TtRR would be TR and tR.
Gametes produced from ttrr would be of only one type - tr.
Possible progenies can be obtained by using Punnett square.
$\begin{array}{cc}\text{Gametes}& \text{tr}\\ \text{TR}& \text{TtRr}\\ \text{tR}& \text{ttRr}\end{array}$
Therefore, TtRr, ttRr are found in the ratio of 1: 1