how do you know if you're a dominant homozygous or heterozygous?

Question

what could you do to figure out your exact genotype?

Answer 1

You might be able to figure it out from the phenotypes of your parents. My blood is type A and so was my dad's. I found out last year when my mom was in the hospital that hers was type O, so now I know I'm heterozygous for my bloodtype.

Also some traits have a different phenotype when you're heterozygous if that characteristic isn't controlled by complete dominance but incomplete or codominance (but not if the trait is controlled by more than one gene).

Answer 2

A test cross with a homozygous recessive (bb). If the parent in question is homozygous dominant (BB) the offspring will all express the dominant gene (only Bb offspring results). If the parent in question is heterozygous (Bb) about half of the offspring will express the dominant gene and about half will express the recessive gene (half the offspring is Bb, the other half is bb).

This can be seen easier if you draw two Punnet squares: one bb crossed with Bb, one bb crossed with BB.

Answer 3

You perform a test cross with someone who displays the recessive phenotype.

Um, this doesn't work very well with humans. Not enough volunteers for those test crosses, and it takes nine months to get the results.