How a testcross can be used to determine if a dominant phenotype is homozygous or heterozygous.?

Question

How a testcross can be used to determine if a dominant phenotype is homozygous or heterozygous.?

Answer 1

Test crosses are done by breeding the individual in question with another individual that expresses a recessive trait of the same character. If all offspring display the dominant phenotype of the trait, then the individual in question is homozygous dominant. If the offspring display both the dominant and recessive phenotypes of the trait, then the individual is heterozygous.

Answer 2

In a test cross, a dominant trait is crossed with a recessive trait. If you want to find if the trait is homozygous or heterozygous, just check the progeny. If all of them are dominant, it indicates that the parent is homozygous dominent. If dominant and recessive off springs are in the ratio 1:1, it indicates that the parent is heterozygous dominant.

Answer 3

a test cross is between a recessive individual and an individual who has a dominant genotype, but an unknown phenotype.

Think of it logically, when the two mate, what does it mean if there are recessive traits in an offspring.

that would mean the dominant, unknown phenotype must be heterozygous.

for example. B stands for brown eyes.

b stands for blue eyes.

if a blue eyed woman (bb) and a brown eyed man (either BB or Bb) mated and produced a brown eyed child (Bb), not much could be infered. But if the child was blue eyed (bb), that means that the Brown eyed male MUST of had the gene for blue eyes- thus being heterozygous.