The ability to roll one\'s tongue into a u-shape is neutralgenetic trait, and is

Question

The ability to roll one's tongue into a u-shape is neutralgenetic trait, and is caused by a dominant allele. If the frequencyof the dominant allele were 0.02, based on the Hardy-Weinbergequilibrium (p2 +2pq +q2, with p+q = 1), whatis the frequency of homozygous normal, heterozygous, and homozygousrecessive individuals? Given these frequencies, how many people inPueblo, population = 103,495, would you expect to be able to roll=their tongues? Since the non-rollin phenotype is recessive, wouldyou expect these folks to decrease in the population over time? Whyor why not?

Explanation / Answer

The frequency of the dominant allele(p) is 0.02. Therefore according to the formula p + q = 1. q = 1-p = 1-0.02 = 0.98. TO know the frequency of the homozygous normal, heterozygous,and homozygous recessive, we use the formula p2 + 2pq + q2 =1 We know that p = 0.02 so p2 = 0.0004 We know that q = 0.98 so q2 = 0.9604 2pq = 2 x 0.02 x 0.98 = 0.0392 0.0004+0.9604+0.0392 = 1. So the formula holds true. To convert these numbers into a % we need to multiply with100. Therefore the frequency of the normalhomozygous [p2]= 0.0004 x 100 = 0.04 the frequency of the homozygous recessive[2pq] =0.9604 x 100 = 96.04 The frequency of the heterozygous[q2] = 0.0392 x100 = 3.92 0.04+96.04+3.92 = 100 So the formula holds true. The given population is 103,495. AS the frequency of the normal homozygous is 0.04 for100. So for 100 the frequency is 0.04 for 103495 it will be 103495 x 0.04/100 = 41.398 AS the frequency of the heterozygous is 3.92 for 100. So for 100 the frequency is 3.92 for 103495 it will be 103495 x 3.92/100 = 4057.004 AS the frequency of the homozygous recessive is 96.04 for100. So for 100 the frequency is 96.04 for 103495 it will be 103495 x 96.04/100 = 99396.598 41.398+4057.004+99396.598 = 103495. IN this population only about 42 people would be able to rolltheir tongues. The allele is recessive but in this population, the number ofhomozygous recessive is the largest. So they may not decrease overtime. The dominant allele may decrease over time as they are only42 out of 103495 people.

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