Question

A couple has three children and ALL of them are Non-tasters of PTC.What is the percentage chance that their next child will also be a Non-taster?

Answer 1

There is a 100% chance the next child is a non-PTC taster. Both parents of the child do not have a dominant PTC gene.

PREMISE 1: A cross between two homozygous recessive parents (genotype tt) will have a 100% chance to have non-PTC taster children.

PREMISE 2: A cross between a heterozygous parent (Tt, PTC taster) and a homozygous recessive parent (tt, non-PTC taster) will have offspring with a 75% chance of non-PTC taster and a 25% chance PTC taster.

PREMISE 3: A cross between two homozygous dominant parents (TT, PTC taster) will have a 100% chance to have PTC taster children.

PREMISE 4: A cross between a heterozygous parent (Tt) and a homozygous dominant parent (TT) will have a 100% chance to have PTC taster children with 75% genotype TT and 25% genotype tt.