Question

A cross was carried out between two pea plants showing the contrasting traits of height of the plants. The result of the cross showed 50% parental characters.
(i) Work out the cross with the help of a Punnett square.
(ii) Name the type of the cross carried out.

Answer 1

	T	t
t	Tt (tall)	tt (dwarf)
t	Tt (Tall)	tt (dwarf)

i) In order to know the parental genotype, we will perform a test cross where the recessive trait is crossed with the parental genotype (which is unknown). As 50% of the parental characters are retained, the parent will be Tt. (The parental genotype TT is not possible as it will give all the plants as tall). The Punnett square with Tt is shown as above.

ii) The type of cross carried out here is a test cross. It is a cross in which an individual with an unknown dominant phenotype is crossed with an individual parent homozygous recessive for that trait.