The ability to roll your tongue is a dominant trait that Alfred Sturtevant observed in 72% of people in a population study. What is the allele frequency of the tongue rolling allele?

Question

aaronq · Answer

Disclaimer: i haven't done this in a while so i could be wrong, but i think this is how it's done. 

Since it's dominant, both, homozygous dominant and heterozygous individuals will carry the allele. ($q$ here is the dominant allele and $p$ is the recessive)

   $q^2+2pq=72\%$

we also know that $p^2=100\%-72\%$

so  $p=\sqrt{.28}=0.5292$

back to the first part: $q^2+2(0.5292)q=0.72$

$q=0.4708$

the frequency of the dominant allele is 0.471