Question

Which of the following represents a test cross in which half the offspring is heterozygous and half would be homozygous recessive?

• A. TT × tt
• B. Tt × tt
• C. Tt × Tt
• D. tt × tt

Answer 1

The Correct Option is B

A test cross is used to determine the genotype of an individual showing a dominant trait. When a heterozygous (Tt) individual is crossed with a homozygous recessive (tt) individual, the offspring will show a 1:1 ratio. Half of the progeny will be heterozygous (Tt), displaying the dominant trait, and the other half will be homozygous recessive (tt), showing the recessive trait.

Answer 2

In a test cross, one of the parents is always homozygous recessive (tt), and the other parent can be either homozygous dominant (TT) or heterozygous (Tt).

• If the cross is Tt × tt, we can predict the offspring's genotypes using a Punnett square. The possible offspring genotypes will be:
• Tt (heterozygous) – 50% chance
• tt (homozygous recessive) – 50% chance

Thus, half of the offspring will be heterozygous (Tt) and the other half will be homozygous recessive (tt).