Question

If 120 plants are produced on crossing pure red and pure white flowered pea plants, then the ratio of offspring will be

• A. 90 red : 30 white
• B. 30 red : 90 white
• C. 60 red : 60 white
• D. All red

Answer 1

Answer: (D)

All red

Genotype of pure red-flowered (dominant) pea plant: RR
Genotype of pure white-flowered (recessive) pea plant: rr
P generation: RR x rr
F${}_1$ generation: Rr (red flowers)
Thus, from a cross between pure red and pure white-flowered pea plants, only red-flowered pea plants are obtained.
Hence, all 120 plants obtained from the given cross are red-flowered plants.

Thus, the correct answer is option D.