Question

An angiosperm plant having red flower when crossed with the other having same colour flower produced 40
progenies, out of which 30 were red coloured flowers, 10 plants were with white flowers. Find out:
(i) What is the possible genotype of parent plants?
(ii) Which trait is dominant and recessive?
(iii) What is the cross called and what is phenotype ratio?

Answer 1

Answer:

(i) Both parent plants are heterozygous for a dominant allele that causes the red colour. The dominant allele is for red flowers (R) and the recessive allele is for white flowers (r), hence the genotype of the parents is Rr.

(ii) Trait 'r' is the recessive trait, whereas trait 'R' is the dominant trait.

(iii) This cross is known as a monohybrid cross because it involves one gene locus, locus for color. Every offspring with a R will have the color red and without R will be white.  As a result, the chance is that 75 percent will be red and 25 percent will be white. That is, for every four children, three will be red and one will be white.

This results in a 75:25 = 3:1 ratio.