Q48 - Tracking Insecticide Resistance Allele Frequency Over Time in Mosquitoes

Theoretical 1 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

Mosquitos are vectors for transmitting human diseases, and the application of insecticides to water bodies is occasionally conducted to control mosquito populations. In a mosquito population, there are two alleles of a locus that affect susceptibility to pesticides, (s): susceptible, and (r): resistant. The resistance is completely recessive. The table below shows the change in the number of individuals with different genotypes before (Pre- 1990), during (1990-2000; shown by an arrow), and after (2005-2015) pesticide application.

Using the information and data, determine which of the statements are true or which are false.

A. No resistance allele was present before insecticide application.

B. During pesticide application, natural selection favored the resistance allele.

C. Resistant individuals (r/r) are likely to have lower fitness than others (s/r, s/s) in the absence of pesticide application.

D. From 1990 to 1995, the frequency of the resistant allele increased more than 10 times.

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Question reproduced from IBO 2020, Theoretical Exam 1, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)