Population Genetics Lab

Based on a lab for Duke University's Introducation to Biological Anthropology and Anatomy

Interactive Population Genetics Model


This lab deals with the processes of genetic drift and natural selection. In small populations genetic drift can be the dominant force in determining the genetic structure of the population. In all populations selection pressures may significantly favor one allele (or combination of alleles) and thus alter the frequencies of alleles within a population. This lab will look at both genetic drift and natural selection and will give students a better understanding of these concepts.

Materials and Equipment


Procedure

  1. Begin by using your hole punch to create small paper dots (or prey) in three different colors.
  2. Distribute the dots to your students (each group of students should get 90 dots (30 each of three different colors), and two different backdrops (one white, blank sheet of paper, and one sheet consisting of multiple colors - the latter sheet can be created by pasting together block of different colored construction paper on one 8.5 X 11 page).
  3. Once the teams have their dots and backdrops, they can begin. The first step is for students to pick a person in their group to be the "predator."
  4. Next the "predator" looks away while the other students place 10 dots of each of the three different colors on the white piece of paper.
  5. After the dots have been placed, the predator will have 15 seconds to pick the first 10 dots that they see. Predators are required to look away after "killing" each dot.
  6. When 10 dots have been killed, one student should record (in a table format) the color and number of surviving dots on the backdrop.
  7. Next, 10 new dots should be added to the board in direct proportion to the colors of the survivors. (In other words, if there are 10 yellow, 4 blue, and 6 green dots surviving, students should add 5 yellow, 2 blue, and 3 green dots. Students shouldn't worry about fractions of dots, crude estimates are okay.)
  8. While the new dots are being added, a new "predator" should be looking away.
  9. This process should be repeated four times. If possible, each student should have a chance to be the "predator" at least once. Finish by adding ten new dots in proportion to those remaining.
  10. Once this simulation is completed the results (number and color of dots left after four generations should be written on the board).
  11. For the next simulation, simply repeat the process on the multicolored backdrop. This represents natural selection, because at least one of the colors will be cryptic on the multicolored backdrop.

Questions to think about......

  1. How do the results for the genetic drift simiulation differ from the natural selection simulation? Which force is more powerful -- genetic drift or natural selection -- in changing phenotype frequencies?
  2. What other factors, besides genetic drift and natural selection might influence allele frequencies in a population?


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