John has a white forelock. His wife Kate has completely brown hair. Their two children (five-year-old Jack and 3-year-old Clara) do not have white forelocks. Their new born daughter Mia is bald, and her hair colour pattern cannot yet be determined. John's mother Liz and his elder sister Jazmin have white forelocks, but his father does not and neither does his younger brother Bikram. Jazmin's husband has uniform hair colour. Both of their fraternal twin daughters (Nora, Lily) have hair like their mother, but their youngest child Jacob, who is adopted, is completely dark haired. Bikram's wife Emma does not have a white forelock, but thinks it is dramatic and hopes to have a child with it someday, especially since her husband's brother has it.
Using conventional symbols, construct a pedigree of the family above, showing the mode of inheritance of white forelock (having a streak of white hair). White forelock (affected) is an autosomal dominant trait. Uniform hair colour (unaffected) is the recessive form of the trait. Indicate the genotypes of the individuals (under the pedigree symbol or in a separate list), and include a legend for your symbols for the phenotypes and genotypes.
Why is the ratio of females with white forelocks to males with white forelocks not 1:1 for this autosomal trait in this pedigree?
What is the probability that a child of Bikram and Emma would have a white forelock? Explain. What is the probability that John and Kate's next child is a girl with a white forelock? Explain.