Question

In humans, the ABO blood type is under the control of autosomal multiple alleles.Color blindness is a recessive X-linked trait.Mom is type A and has normal color vision.Dad is type A and has normal vision.They have a son who is type O and is color-blind.What is the probability that their next child will be a daughter who is type O and has normal color vision?Enter your answer as a fraction (for example: 1/5).

Answer 1

Answer: 1/4

Explanation:

Firstly, in order for both parents to be type A and have children with type o blood, their blood types must both be Ao. Since o is a recessive blood type, a punnett square shows there is a 25% chance any child of theirs will have type o blood. If neither parent is color blind and they have a son who is, it implies that the mother is a carrier of colorblindness and has the genotype XᴮXᵇ. If you do a punnett square of the not colorblind father (XᴮY) and the mother, it shows that a daughter would have a 0% chance of being colorblind. Therefore colorblindess is irrelevent, since there is no possibility of the daughter not having normal color vision. In conclusion, there's a 25% chance she will have type o blood and not be colorblind, since the other 75% chance would be having type A blood and not being colorblind.