Question

In genetics the term test cross means

• A. the crossing of $F_1$ individual with homozygous recessive.
• B. crossing an $F_1$ individual with either of the two parents.
• C. crossing $F_1$ individual with another $F_1$ individual.
• D. crossing $F_1$ individual with that of $F_2$.

Answer 1

Answer: (A)

A test cross is a cross involving the mating of $F_1$ individual with the homozygous recessive parent. It is done to find out homozygous and heterozygous individuals. The off springs will be $100\%$ dominant if the individual was homozygous dominant and the ratio will be $50\%$ dominant and $50\%$ recessive in case of hybrid or heterozygous individual. Here, $AaBb$, should be crossed with $aabb$. As $aabb$ will produce only one type of gamete thus difference in traits if observed in their progenies will be due to the different gametes produced by hybrid dominant parent. This will indicate the genotype of the dominant parent.