Question

Given a plant with the genotype C/c^m; Ac⁺/Ac⁺, where c^m is an unstable allele caused by a Ds insertion. This plant is crossed with another plant with the genotype C/c^m where c^m is an unstable allele caused by Ac insertion.

What phenotypes would be produced (including their proportion)? Assume that Ac and c are unlinked, that the chromosome-breakage frequency is negligible, and that mutant c/C is Ac+.

Answer 1

Answer)

According to Ac-Ds system:

Ac is an unstable allele autonomous ;

Ds is revert only in the presence of Ac and non-autonomous, Hence Ac+ indicates the absence of the Ac regulator gene

Cross 1:

P : C/c Ds : Ac/Ac + X c/c : Ac+ / Ac +

F1 generation: 1/4 C/c : Ac/Ac+ (solid pigment)

   1/4 C/c : Ac+/Ac+ (solid pigment)

1/4 c Ds /c: Ac/Ac+ (unstable colorless)

1/4 c Ds /c: Ac/Ac+ (colorless)

Therefore, 2 solid : 1 spotted : 1 colorless

Cross 2:

P: C/ c Ac X c/c

F1 generation: 1/2 C/c (solid pigment)

   1/2 C/c Ac (unstable colorless)

Therefore, 1 solid : 1 spotted

Cross 3:

P: C/c Ds : Ac / Ac +    X C/c Ac : Ac+/ Ac+

F1 generation: 1/8 C/C : Ac/Ac+ (solid pigment)

1/8 C/c : Ac / Ac+ (solid pigment)

1/8 C/C : Ac+/ Ac+ (solid pigment)

1/8 C/c Ac : Ac+/ Ac+ (solid pigment)

   1/8 C/c Ds : Ac+/ Ac+ (solid pigment)

1/8 C/c Ds : Ac +/ Ac (solid pigment)

1/8 c Ds /c Ac : Ac+/ Ac+ (spotted)

1/8 c Ds /c Ac : Ac+ / Ac (spotted)

Therefore, 3 solid : 1 spotted