Albinism is a condition in which pigmentation is lacking. In humans, the result is white hair, non-pigmented skin, and pink eyes. The trait in humans is caused by a recessive allele. Two normal parents have an albino child. What are the parents' genotypes? What is the probability that the next child will be albino?

1/4 or 25% chance / probability of having an albino child.

Explanation:

Albinism is a recessive trait, this means that a person need 2 copies of the allele to express this condition. If both parents are normal their genome must be Aa ("A"=normal condition and "a" recessive allele) when they produce gamets they could either be "A" or "a" but when fertilization happens there's a 25% chance of 2 gametes with the recessive trait to meet, hence producing an albino.

It is important to understand that this is only probability. A couple could have 6 children and all of them could be normal.