1 In shorthorn cattle a red animal crossed with a white anim

1. In shorthorn cattle, a red animal crossed with a white animal gives all roan in the F1 generation. Give the genotypic and phenotypic ratio that will result from crossing roan offspring of the F1 generation.

2. If a child’s blood type is A and the mother’s blood type is O, what blood types might the father have? What are the possible genotypes of the father?

Explain your answers.

Solution

1.   If we cross red animal with a white animal

RR (red) x WW (white)         [Parents]

Rw (roan)                                [F1 ]

Rw   x    Rw                           [F1 self cross]  

Gametes

R

W

R

RR        red

RW      roan

W

RW         white

WW       white

So in the F2 generation we get 1:2:1 for the ratio of genotypic and phenotypic both. This is the case of Incomplete dominance..

2.   If mother’s blood group is O then her configuration is I^O I^O

Child has blood group A, so the configuration is I^A I^A or I^A I^O

Look the table down:

Father blood

I^O   [Mother]

I^A

I^A I^O [A blood group]

So if father must contain one gamete of I^A, he may have one of I^A I^A, I^A I^O or I^A I^B blood types; which provide A, A and AB blood groups respectively. In these possibilities, one gamete contains I^A.