Question You want to determine the zygosity of a parent plan

Question:

You want to determine the zygosity of a parent plant that shows the dominant phenotype for the trait, Q.

Which of the following could represent a test cross to determine the genotype of that plant?

Select all that are correct.

A)   QQ x Qq

B)   qq x qq

C)   Qq x qq

D) qq x QQ

E) QQ xQQ

F) Qq xQq

Solution

Test cross is carried out to know whether the plant is homozygous dominant or recessive or heterozygous for the given trait. The plant with known genotype, most probably homozygous recessive is crossed with unknown genotype. The unknown genotype may be homozygous dominant or heterozygous for the given trait.

Crossing between plants with genotypes qq X QQ or qq X Qq are mostly carried out test crosses. Options C and D are correct.