I'm studying modified Mendelian ratios. I've got a theoretical problem that I'm stumped on:
A species of bird may have normal wings, or a mutation that causes frazzled wings.
I do 15 identical breeding pairs, crossing a male bird with frazzled wings to a normal winged female. The progeny obtained are 46 with normal wings (22 male/24 female) and 23 frazzled, all male.
Afterwards, I mate the normal winged females to the normal winged males obtained from the above cross. The progeny obtained all have normal wings.
I figured out a possible solution, and would like to know if it makes sense:
Z(f) = Z sex chromosome with normal wing gene, recessive
Z(F) = Z sex chromosome with frazzled wing gene, dominant
W = W sex chromosome
Z(F)/W= abnormal wing female bird (does not survive as not enough gene product produced)
Z(f)/W= normal wing female bird
Z(F)/Z(F)= abnormal wing male bird (does not survive as not enough gene product produced, or possibly survives as just enough is produced by 2 mutant genes, doesn't matter anyway)
Z(F)/Z(f)= abnormal wing male bird (survives as wildtype gene produces enough product)
Z(f)/Z(f)= normal winged male bird
Z(F)/Z(f) × Z(f)/W
Z(F)/W (fails to survive),
Z(f)/W in 2:1 normal:frazzled wings
Z(f)/Z(f) × Z(f)/W produces
This would account for the phenotypic ratios seen in the problem, and also uses the
ZW sex chromosome system found in birds. The genetic explanation would be that a single
Z(F) does not produce enough product to thrive, for whatever reason. The trait is sex-linked dominant on the Z chromosome.