Question

Explain how heterozygote inferiority can lead to greater genetic diversity among populations. Use the results of Foster et al.’s experiment with fruit flies as an example. (based off of ch6 and 7 of evolutionary analysis 5th edition)

Answer 1

foster and colleagues set up an experiment to demonstrate that the hetrozygote inferiority lead to genetic diversity among population.They experimented on fruit flies in which some are heterozygotes having lower fitness than homozygotes. they used compound chromosomes( compound chromosomes are homologous chromosomes). during meiosis of compound chromosome, four kind of gametes are produced: gametes with both homologous chromosomes, gametes with one member of the pair, gametes with other member of pair and gametes with no chromosomes. During meiosis of normal chromosome, only one kind of gametes are produced: gametes having one member of heterologous chromosome. foster and colleagues did two types of crosses: one cross is between two flies having compound chromosome and other cross is between two flies in which one fly with compound chromosome and other fly with normal chromosome.

According to experiment when two flies with compound chromosome mate only one fourth population is viable and when two flies in which one with compound chromosome and other with normal chromosome mate none of the zygote is viable.foster et al established two set of population: one having compund second chromosome and other having compound third chromosome. when two flies one having copmound second chromosome and other having compound third chromosome mate none zygote is viable.

foster did experiment up to 13 mixed population and they found that population with higher compound second chromosome quickly rose to fixation and poupulation with lower compound second chromosome was quickly lost. By this he defined the fitness of the population.Population with homologous chromosome will survive.So foster experiment demonstrate that by driving different alleles to fixation in different population,heterozygotic inferiority may help maitaining the genetic diversity.