Question

Amoeba Sisters Video Recap: Alleles and Genes
Deducing a Genotype: If assuming PTC as a simple gene trait,
what other genotype would you select to put in this missing
genotype box that could result in this phenotype? Why

Answer 1

PTC tasting is usually treated as a simple dominant trait (T = taster, t = non-taster).

- If the phenotype shown is "taster," the missing genotype could be either TT or Tt.
- I would pick Tt as the other genotype because it still gives the taster phenotype (dominant T expresses even when only one copy is present) but is genetically different from TT and can explain why a non-taster (tt) might appear in offspring.
- If the phenotype shown is "non-taster," the only genotype that fits is tt, because the recessive phenotype requires two recessive alleles.

So: choose Tt for a taster phenotype (or TT also works), and choose tt for a non-taster phenotype — because dominant alleles mask recessives, and recessives require two copies.