Question

Two individuals that are heterozygous for tongue rolling mate. What are the predicted genotypic and phenotypic ratios for this cross?

Answer 1

Genotypic ratio = 1:2:1

Phenotypic ratio = 3 tongue rollers : 1 non-tongue roller

Step-by-step explanation:

This question involves a gene coding for the ability to roll the tongue or not in humans. The allele for tongue rolling (R) is dominant over the allele for non-tongue rolling (r).

According to this question, two individuals that are heterozygous for tongue rolling mate i.e. Rr × Rr. The proportion of offsprings that will be likely produced from this cross will be: RR, Rr, Rr, and rr.

- Offsprings with RR, Rr, Rr are tongue rollers

- Offsprings with 'rr' are non-tongue rollers.

Hence, the predicted genotypic and phenotypic ratio are as follows:

Genotypic ratio = 1 RR :2Rr :1rr

Phenotypic ratio = 3 tongue rollers : 1 non-tongue roller