Biological problems in high school about hereditary diseases. Who can tell me about it?

(1) albinism is an autosomal recessive genetic disease. According to the meaning of the question: Xiao Li suffers from albinism, but Xiao Li's parents have normal phenotypes, so we know that both parents are gene carriers that cause albinism. That is, they are all heterozygotes. If A is a normal gene, A is an albino gene, and its parents' genotypes are Aa. If the sister's phenotype is normal, her genotype may be (2)Aa or (1)AA (drawing genetic map), then the possibility of carrying albino gene is 2/3.

(2) Xiao Li's sister is married to a normal person, and their first child suffers from this disease, so we can know that their genotypes are all Aa, so the probability that the second child also suffers from this disease is 1/4.

(3) Xiao Li's sister married an albino. According to the first question, her sister's genotype is (2/3)Aa or (1/3)aa, and only (2/3)Aa and Aa (albinos) will have sick children. Probability = 2/3 * 1/2.