Question

For the same cross: BbTt x bbTt a. Using the Probability Method illustrated in lecture, break the complex two-gene cross into two simple single-gene crosses (note that the Probability Method can be used if it is known that the alleles of the different genes Assort Independently) b. Show the expected genotypic and phenotypic ratios for each of the simple single-gene crosses.

Answer 1

Answer and Explanation:

cross: BbTt x bbTt

Cross for B gene

Parental ) Bb x bb

Gametes) B b b b

Punnet square) B b

b Bb bb

b Bb bb

F1) Genotypic proportion: 2/4=1/2 Bb : 2/4=1/2 bb

Genotypic ratio 1:1

Phenotypic proportion: 2/4=1/2 B- : 2/4=1/2 bb

Phenotypic ratio 1:1

Cross for T gene

Parental ) Tt x Tt

Gametes) T t T t

Punnet square) T t

T TT Tt

t Tt tt

F1) Genotypic proportion 1/4 TT

2/4 Tt

1/4 tt

Genotypic ratio 1 : 2 : 1

Phenotypic proportion: 3/4 T-

1/4 tt

Phenotypic ratio 3 : 1