Genetic Trait Mystery: Nina's PTC Tasting Dilemma

Why is Nina a Non-Taster in a Family of Tasters?

Can you help Nina solve this dilemma by filling in the pedigree chart for the possible phenotypes of Nina's family tree with respect to the PTC trait? Color in the boxes and circles to show individuals with the trait, carriers of the trait, and whether they are a taster, non-taster, or a carrier.

Final answer:

PTC tasting is a genetic trait where the ability to taste PTC is dominant. If both parents are tasters but their child is a non-taster, the parents must be carriers of one non-taster allele each. Other family members could be either TT or Tt without further testing.

Explanation:

The trait of PTC tasting is governed by a single gene with two alleles: a taster allele and a non-taster allele. The taster allele is dominant, meaning you only need one copy of this allele to taste PTC. Nina not tasting PTC indicates she carries two non-taster alleles.

For her family members, who are all tasters, they could either be TT (two taster alleles) or Tt (one taster allele, one non-taster allele - a 'carrier')

Given that both of Nina's parents are tasters, but she is a non-taster, her parents must both be Tt. This means that they each passed one non-tasting allele to Nina, resulting in her being tt. Similarly, for Nina's brothers, grandparents and aunt and uncle, we can't definitively say if they are TT or Tt without further information, but they are all at least carriers of the taster allele.