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

Hint: Hybridization is the process by which we can get the required characteristics of the plants in their next generation. Gregor Johann Mendel proposed some laws to explain patterns of inheritance in plants. He took a pea plant for his experiments, working on seven types of characters including height of the plant, color of a flower, color of pod, shape of pod, shape of seed, color of seed, and position of flower.

Complete answer:
According to G.J Mendel, each gene can have two or more alternative forms called alleles out of which one is dominant and the other is recessive. In this question, we have to find out the ratio of offsprings when pure red (RR) and pure white (rr) pea plants are crossed. We will denote the gamete of the pure red flower by R and the gamete of the pure white flower by r. The cross between these two plants is shown below by Punnett square:

	R	R
r	Rr	Rr
r	Rr	Rr

All the plants in the F1 generation will be heterozygous dominant. This can easily define that we will get all plants red flowered because in every offspring there is a dominant allele expressing red color.
So, the correct answer to this question is option (D)-All red.

Note: According to the law of dominance given by Mendel the cross between pure homozygous dominant and homozygous recessive plants, always results in the heterozygous offsprings. Hence, all offsprings, in this case, will be red colored because red is the dominant trait. If the red flowered plant would be heterozygous dominant, the ratio would be 1:1.