Question

The dihybrid test cross ratio is

• A. 9 : 3 : 3 : 1
• B. 3 : 1
• C. 1 : 1
• D. 1 : 1 : 1 : 1

Answer 1

Answer: (D)

1 : 1 : 1 : 1

A test cross is performed to determine the genotype of a dominant parent if it is a heterozygous or homozygous dominant. For the purpose, a dominant parent is crossed with the homozygous recessive parent. A test cross between $F_1$ dihybrid and homozygous recessive dihybrid gives 1:1:1:1 ratio. Whereas selfing of dihybrid produces 9:3:3:1 ratio in the $F_2$ generation and 3:1 ratio is obtained by self-pollination of monohybrid $F_1$ progeny. A monohybrid test cross between $F_1$ hybrid and the homozygous recessive parent gives 1:1 ratio.

Thus, the correct answer is option D.