In a dihybrid cross AAbb x aaBB what proportion of homozygot

In a dihybrid cross AAbb x aaBB, what proportion of homozygotes is expected among the F2 offspring? Please explain how you got the answer!

Solution

Dihybrid cross.......AAbb x aaBB.......gametes.......Ab, aB F1 cross.............. Ab Ab aB AaBb AaBb aB AaBb AaBb The F1 cross results in 100% heterozygotes.........AaBb Upon selfing of F1 hybrids................... AaBb x AaBb (gametes are AB,Ab,aB,ab) Four possible combinations could be found. 25% of AB gametes, 25% of Ab gametes, 25% of aB gametes, 25% of ab gametes could be found in this heterozygous dominant cross. AB Ab aB ab AB AABB AABb AaBB AaBb Ab AABb AAbb AaBb Aabb aB AaBB AaBb aaBB aaBb ab AaBb Aabb aaBb aabb 16 possible combinations could be formed. Homozygous for both recessive characters............aabb homozygous for both dominant characters.............AABB aabb has been 1/16 of possible combinations AABB has been 1/16 of possible combinations Thus proportion of homozygous for both recessive traits and homozygous for both dominant characters among the F2 offspring has been........... 2/16