Multiple choice . Marta and Josiah produced a child with Tay-Sachs, so both Marta and Josiah must be Tt . Therefore both Jessica and Mateo have a 50-50 chance of receiving the t allele. The correct answer is b. The other crosses will not produce the desired result of all barred in one sex and all nonbarred in the other sex.
Brother has ss , so both parents have s allele.
Based on blood type only, Ringo and John could go with either set of the remaining parents. Pedigree drawn in review session, or see me if you have questions. If the first child is pp , then William and Jasmine must both be Pp . Pedigree drawn in review session, or see me if you have questions. Two genes on the X chromosome influence red-green colorblindness.