Names____________________________________________________________
Biology
Genetic Drift Lab
Date_______________________ Per_____
Purpose:
This lab will help demonstrate the idea of genetic drift, which is when traits become more or less common in a population over time
by random chance. In this case we are looking at one population: insects of the species Beanus Familiarus. The Beanus Familiarus
insects can be one of four different colors, depending on the alleles they have. They can be orange, green, red and purple.
During the lab there will be 5 generations. During each generation, events will happen and the population will change. You will keep
track of how allele frequencies change within the gene pool of the population.
Materials:
Insects:
1. Red beans
2. Green beans
3. Purple beans
4. Orange beans
Other materials:
1. Brown bag
2. Dead Insects Cup
Procedure:
1 Place 5 of each color of insect in the brown bag
2
Shake the bag to mix up the population.
3
10 randomly colored insects are consumed by predators. Reach into the bag and pull out eight insects without looking.
4
Calculate how many insects are still alive of each color and record in “Number Alive”
5
Do not throw the insects that were eaten back into the bag. Put them into your “Dead Insects cup.”
6
Each insect that survived will produce one offspring. Add the offspring insects for each color to the brown bag. You can take
insects from your “Dead Insects Cup” or the plastic bags to do this.
Add up the number alive after reproduction (it should be double the “Number Alive”) and record it in “Number Alive After
Reproduction” in your Insects Data Table.
7
8
Repeat steps 3-7 until you’ve gotten through 4 generations.
9
Go back and calculate the allele frequencies each generation:
Allele frequency = # of that color insect alive / total number of insects alive
Insects Data Table
Insect Numbers
Example
Generation 0
Generation 1
Red
Orange
Purple
Green
Total
Starting Number
5
5
5
5
20
Starting Allele
Frequency
5/20=
5/20=
5/20=
5/20=
.25
.25
.25
.25
Number Alive
Number Alive After
Reproduction
Allele Frequency
= # of that color insect
alive / total number of
insects alive after
reproduction
Generation 2
Number Alive
Number Alive After
Reproduction
Allele Frequency
= # of that color insect
alive / total number of
insects alive after
reproduction
Generation 3
Number Alive
Number Alive After
Reproduction
Allele Frequency
= # of that color insect
alive / total number of
insects alive after
reproduction
Generation 4
Number Alive
Number Alive After
Reproduction
Allele Frequency
= # of that color insect
alive / total number of
insects alive after
reproduction