Question

Red is dominant over white in a certain flower. Which of the following helps to test whether a red offspring is homozygous or heterozygous in this flower?

• A. Cross it with a red plant that had a white parent
• B. Cross it with a red plant that had two red parents.
• C. Cross it with a white plant.
• D. Two of the above will work.
• E. None of the above will work.

Answer 1

The correct option is C Cross it with a white plant.

A test cross is a cross in which F${}_1$ generation is crossed with the homozygous recessive parent. This test is useful to know the zygosity of the former by analyzing the proportions of offspring phenotypes. Zygosity can be either heterozygous or homozygous.

To know whether red offspring produced is homozygous or heterozygous, it should be crossed with a white plant.

So, the correct option is 'Cross it with a white plant'.