In the third stage, a yellow (Aya) mouse was crossed with another yellow (Aya) mouse, resulting in 1 dead (AyAy), 2 yellow (Aya) and 1 meto (aa) mice.
here,
The genotype of yellow mice is Aya
Parents : ♂ × ♀
Phenotype: Yellow Yellow
Genotype : Aya Aya
Gamit : (Ay) (a) (Ay) (a)
F2 progeny (checker board)
Remarks : From the checker board, out of 4 rats, 1 is dead, 2 are yellow and 1 is meto colored. The mouse died because the expressed gene Ay was homozygous (AyAy).
Phenotypic ratio : Yellow : Meto = 2 : 1