Changes in single gene allelic frequencies under a varying selective pressure
- Conduct an optional computer lab-based simulation activity to illustrate the changes in single gene allelic frequencies under a varying selective pressure.
- Help the students to plot graphs depicting the changes in allele frequencies through the generations.
- Discuss with the students how a climate related change in environment could play a role in changing the allelic frequencies for the given gene.
This activity can be used to extend the understanding of natural selection by the observations of changes in allelic frequencies over successive generations, due to an adaptive advantage for varying selective pressures. Use the simulation, 'Natural Selection' to explore how the allelic frequencies for a single gene, that codes for body colour, changes through several generations when a varying selection pressure (different environments) is applied.
Launch the simulation and follow the instructions to run it. Select an initial allelic frequency for alleles 'A' and 'a' of a gene for body colour in a starter population of insects, for a given Click the 'Natural Selection' tab and then the 'Generation' button, in order from G1 to G5. Record the data generated in table for changes in allelic frequencies over five generations.
Use the 'Reset' button and repeat this activity for different allelic frequencies of the starter population for a varying environment. End-point allelic frequencies can also be compared by varying the allelic frequencies at the start for a given environment.
Try to plot graphs depicting the changes in allele frequencies through the generations. If needed, try to use the worksheet to record the observations and fill in answers to the journal questions to provide explanations for the observations.
- This exercise will help to observe the changes in allelic frequencies over successive generations. Discuss if an allele is associated with an adaptive advantage, its frequency will increase in a population and may eventually get fixed while an allele that does not have an advantageous adaptive trait, will decrease in frequency and may eventually be lost from the population. Finally, extend your thinking by discussing how a climate related change in environment could play a role in changing the allelic frequencies for the given gene.