Bootcamp Bio test #5 question 34

[cacajuate]

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A father with type B blood and a mother with type O blood have a child with type O blood. What is the probability that their next child will have type O blood?

It says the answer if 50% but wouldn't it be 33%? Question says that they already have a child with type O blood, so if they already have one that would mean only 1 out of the next 3 have a chance of getting type O blood. How come we factor in the child they already had when it says the probability of their next child?

 

[FeralisExtremum]

Question says that they already have a child with type O blood, so if they already have one that would mean only 1 out of the next 3 have a chance of getting type O blood. How come we factor in the child they already had when it says the probability of their next child?

The genotype of the existing child has no impact on anything whatsoever. Just set up a simple Punnett square: BO (father) x OO (mother). 50% chance of OO for the next child.

 

[cacajuate]

Ok, I just thought the wording was asking for whats coming next. Thanks