Genetic Drift Lab

Genetic Drift Lab

When together in the classroom, we use M&Ms to demonstrate the concept of genetic drift because these candies are easy to work with and come in a variety of colors. However, you can easily do this lab from the comfort of your home using three numerous, small items you have laying around your house (edible or not). For example, you could use three different kinds of cereal, candy, nuts/dried berries, marbles, washers/screws/nails, buttons, etc. The key here is that you will need three easily distinguishable phenotypes that you can sample, sort, and count.

What you’ll need to gather:

· Approximately 75 pieces total of three different items (if possible, 25 of each item). These 75 pieces together represent your “original” population. Each item in this original population represents an allele.

· A calculator

· Your notes on genetic drift

1. What three phenotypes (items) did you choose? Record these in the phenotype column of the table below. Count the number of different alleles and record the values in the original population # of pieces column. Calculate the proportion that each allele contributes to the genetic make up of the original population and record these values in the corresponding % column.

You will now take a sample from your original population. Mix together all your items and without looking, pull out and set aside approximately 40 pieces. This is your trial sample #1. Count out the number of different alleles in this trial sample. Record the values under the Trial #1 column. When you are finished counting and calculating the proportions, return this trial sample back to the larger, original population.

Repeat this sampling process for trials 2 and 3.

2. How do the proportions of alleles in your trial samples (1–3) compare to the proportions of alleles in the original population? Describe.

You will now repeat this sampling process again. Without looking, set aside approximately 10 pieces. This is your trial sample #4. Count out the number of different alleles in this trial sample. Record the values under the Trial #4 column. When you are finished counting and calculating the proportions, return this sample trial back to the larger population.

Repeat this sampling process for trials 5 and 6.

3. How do the proportions of alleles in your trial samples (4–6) compare to the proportions of alleles in the original population? Describe.

4. Compare the outcomes of your trials between both tables. Was there a greater effect on the larger or smaller trial samples? Why do you think this occurred?

5. Pick one of your trials from the above table. Individuals with these alleles have migrated out of the original population permanently and become reproductively isolated. This is a special case of genetic drift called ________________________________.

6. Do the alleles of this new isolated group accurately reflect the alleles of the original population? Given enough time and continued isolation, what would this new population potentially evolve to look like?