Question

You are given tall pea plants with yellow seeds whose genotypes are unknown. How would you find the genotype of these plants? Explain with the help of a cross.

Answer 1

Perform a test cross with a double-recessive plant, ttyy. Let the unknown plant be T_Y_. If it is TTYY, all offspring are tall-yellow. If heterozygous at both loci (TtYy), the cross TtYy × ttyy gives four phenotypes in a 1 : 1 : 1 : 1 ratio. The progeny reveal which dominant alleles are heterozygous.