A man and woman are both heterozygous for the recessive allele that causes cystic fibrosis. What is the probability that their first two offspring will have the disorder?

The three genes X, Y, and Z are linked on an autosomal chromosome in humans (X to Y is 15 cM, and Y to Z is 18 cM). If an individual that is heterozygous at all three loci (XYZ/xyz) has children with an individual that is homozygous recessive at all three loci (xyz/xyz), what is the probability that they will have a child that is phenotypically identical to either parent (X-Y-Z- or xxyyzz)? Assume there is no genetic interference to double crossover events at this site.

Hypophosphatemia (vitamin D-resistant rickets) is inherited as a sex-linked dominant trait (H). A) A normal woman and a man with hypophosphatemia marry. What is the chance of having daughters with rickets? Sons? B) A heterozygous woman and a normal man marry. Does the mother have rickets? What is the chance of having daughters with rickets? Sons?

A couple finds out that both the male and the female are heterozygotes (carriers) for Tay Sachs. Draw a punnet square for this couple. What is the likelihood that this couple will have an offspring with Tay Sachs?

A male with autosomal dominant brown hair and a female with unknown hair color have 3 sons with recessive blonde hair. What is the male’s genotype?  What are the possible genotype(s) and phenotype(s) [hair color] of the female?