Question

__________ is used to determine whether an individual expressing the dominant phenotype is homozygous dominant or heterozygous.

A. A test cross
B. A monohybrid cross
C. A dihybrid cross
D. A Punnett square

Answer 1

A test cross is performed to determine if an individual with a dominant phenotype is homozygous dominant or heterozygous, by crossing it with a homozygous recessive individual and analyzing the F1 offspring's phenotypes.

Step-by-step explanation:

A test cross is used to determine whether an individual expressing the dominant phenotype is homozygous dominant or heterozygous. The correct option is A. A test cross.

In a test cross, the individual with the dominant phenotype (unknown genotype) is crossed with an individual that is homozygous recessive for the same trait. If the dominant-expressing individual is homozygous dominant, all F1 offspring will display the dominant phenotype. Conversely, if the individual is heterozygous, the F1 offspring will show a 1:1 phenotypic ratio of dominant to recessive individuals. This technique, introduced by Mendel, helps clarify the genotype of an organism expressing a dominant trait.