Q. In water melon, red fruit colour (R) is dominant over cream fruit colour (r). A water melon plant homozygous for red fruits is crossed with a plant homozygous for cream fruits. The F1 are intercrossed to produce F2. (a) Give the genotypes and phenotypes of the parents, the F1, and the F2. (b) Give the genotypes and phenotypes of the offspring of a backcross between the F1, and the red fruit colour homozygous parent. (c) Give the genotypes and phenotypes of a backcross between the F1, and the cream fruit colour homozygous parent.
Answers
Answer:
(a) The genotype of a parent which is homozygous for red fruits would be RR.
The genotype of a parent which is homozygous for cream fruits would be rr.
Thus, the cross would produce offspring (F₁ generation) with genotype Rr that is, heterozygous for fruit color. As red is a dominant trait thus, the phenotype of all the individuals of F₁ generation would be red fruits.
The genotype of F₂ generation produced by inter-crossing the individuals F₁ generation would be RR, Rr, and rr in 1:2:1.
Thus, the phenotypes would be red fruits (RR and Rr) and cream fruits (rr).
(b) Cross between F₁ individual (Rr) and homozygous red fruit plant (RR) would result in the production of offspring with two types of genotypes RR and Rr. However, the phenotype would remain the same that is, red fruits.
(c) Cross between F₁ individual (Rr) and homozygous cream fruit plant (rr) would result in the production of offspring with two types of genotypes Rr and rr.
The phenotype of offspring with Rr would be red fruits and that of rr would be cream fruits.
