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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.
Solution
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 | |
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