1. A child is born with a sex-chromosome aneuploidy, XXYY, from karyotypically normal mom and dad. The child has asthma related to a gain of function (GOF) mutation in the ILR9 gene in the pseudo-autosomal region of the sex chromosomes. The father has mild asthmas symptoms and the mother has none.
a) What is the genotype of the mom for the ILR9 gene?
b) What is the genotype the dad for the ILR9 mutant? Consider if there’s more than one possibility.
c) Draw out the meiotic event(s) that could result in the child described above. If there is more than one scenario in which this could happen, try to draw out each possibility. Show any crossing over events that lead to homologous recombination.
d) What could the genotype of the child for the ILR9 mutant be? State when the NDJ happened and in what parent AND if homologous recombination is necessary to create the gamete that forms this child. If there’s more than one possibility include others as well, related to your drawings if possible.
e) Is this child likely to be identified as a boy or girl at birth? Why?
f) Would X inactivation influence the asthma phenotype of a woman that is Xa-Xa+?