Campbell Biology (11th Edition)

Published by Pearson
ISBN 10: 0-13409-341-0
ISBN 13: 978-0-13409-341-3

Chapter 23 - 23.2 - Concept Check - Page 491: 3


This population could be evolving as the described genotype distribution at this locus is not at Hardy-Weinberg equilibrium.

Work Step by Step

To determine this from the given data, we calculate whether the population is at Hardy-Weinberg equilibrium. Equilibrium would indicate that the population is not evolving. 120 organisms with two alleles each is a total of 240 alleles. 124 are V alleles. 116 are v alleles. For V: $p = \frac{124}{240}=0.52$ From v we can do two things: we can calculate the frequency as above, or we can use the above-calculated frequency of V. Since the frequencies of both V and v must add to one: $1-0.52=0.48$ We can then use these allelic frequencies to determine if the population is at Hardy-Weinberg equilibrium. To do this, we use the above-calculated frequencies to determine the expected equilibrium genotype distribution. For VV: $p^2=0.52\times0.52=0.27$ $120\times0.27=32$ organisms of genotype VV For Vv: $2pq=0.52\times0.48=0.5$ $120\times0.5=60$ organisms of genotype Vv For vv: $q^2=0.48\times0.48=0.23$ $120\times0.23=28$ organisms of genotype vv Since the actual observed genotypes in this population do not match the expected numbers at equilibrium, this population is not at Hardy-Weinberg equilibrium and should be evolving.
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