In humans, there is a gene that controls the formation of muscles in the tongue that allow people with those muscles to roll their tongues, while people who lack those muscles cannot roll their tongues. The ability to roll one's tongue is dominant over non-rolling. Which ratio accurately represents the genotypes of the offspring that would result between two heterozygous rollers? 1:2:1 3:1 1:1:1:1 1:1

1:2:1

Explanation:

This question involves a gene coding for the possession or not of the muscle that confers the ability to roll one's tongue. The allele for ability to roll (R) is dominant over the allele for non-ability to roll (r).

According to this question, two heterozygous rollers (Rr) were crossed. The following gametes will be produced by each parent;

Rr - R and r.

Using these gametes in a punnet square (see attached image), the following proportion of offsprings will be produced: RR, Rr, Rr, and rr.

Since RR (1), Rr (2) and rr (1) are of three different genotypes, the genotypic ratio of the offsprings will be 1:2:1.

this is true, assuming that the allele is completely recessive and incomplete dominance is not a factor.