Question

A test cross distinguishes between:

• A. two homozygous forms
• B. a homozygous dominant and heterozygous form
• C. two heterozygous form
• D. a homozygous recessive and heterozygous form

Answer 1

Answer: (B)

Test cross can be defined as the cross in which an organism is crossed with other organism having recessive phenotypic trait (recessive homozygous genotype). In the monohybrid test cross, the ratio is 1:1 while in a dihybrid cross, the expected ratio is (1:1) (1:1)= 1:1:1:1. If the ratio of a monohybrid cross is not 1:1 then the crossed organisms must be heterozygous. Thus, the test cross is performed to distinguish between the homozygous dominant and heterozygous form.

So, the correct answer is option B, a homozygous dominant and heterozygous form.