You are a farmer that grows corn. You are offered a genetically modified variety of corn that is 100
percent resistant to corn borers. You have to decide what proportion of your field you should plant in
resistant corn versus a variety that is susceptible to corn borers. Explain why you might choose one of
the following proportions of resistant to susceptible: 100:0, 90:10, 75:25, or 50:50.
What will be an ideal response?
The ultimate answer depends on rates of selection pressure associated with the resistant variety of
corn. The question should be studied using methods of population genetics. Some variables to consider
are: Is the yield of resistant and susceptible corn the same in the absence of corn borers, and in the
presence of corn borers? What is the probability the corn borer will evolve resistance to the new
variety of corn, which in part depends on the population genetics of the system? In effect, if the corn
borer population contains a lot of genetic variability (highly heterozygous) then planting at the higher
proportions of resistance will reduce rates of evolution.
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