In: Biology
Dimples is dominant over smooth cheeks, and brown eyes are dominant to blue. A blue-eyed woman with dimples (both her parents had brown eyes, her mother had dimples and her father had no dimples) marries a brown-eyed man with dimples (his father had blue eyes and dimples, his mother had brown eyes and no dimples). What is the probability that their first child will have blue eyes and dimples?
a. |
1/4 |
|
b. |
1/2 |
|
c. |
3/8 |
|
d. |
3/4 |
|
e. |
1/8 |
let the alleles be D- dimples d- no dimples, B-brown eyes, b- blue eyes.
the genotype of the blue-eyed woman with dimples is bbDd, ( since her father had no dimples, the father's genotype is dd so she inherited d allele from her father since the blue eyes is a recessive trait the genotype is bb)
the genotype of the brown-eyed man with dimples is BbDd ( since the father had blue eyes, he has inherited the b allele from the father, since he has brown eyes he has dominant B allele, so genotype is Bb, mother have no dimples so her genotype is dd, so he has inherited d allele from mother since he has dimples he has the dominant allele D so his genotype is Dd)
bbDd * BbDd
BD | Bd | bD | bd | |
bD | BbDD (brown eyes, Dimples) | BbDd ( Brown eyes, Dimples) | bbDD ( Blue eyes, Dimples) | bbDd ( Blue eyes, Dimples) |
bd | BbDd ( Brown eyes, Dimples) | Bbdd (Brown eyes, no dimples) | bbDd ( Blue eyes, Dimples) | bbdd ( Blue eyes, no Dimples) |
the probability that their first child will have blue eyes and dimples = number of children with blue eyes and dimples/total number=3/8
so the answer is c) 3/8