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Understanding a Gene Pool
You will make a model gene pool based on an initial assumed population, collect data to test the
Hardy-Weinberg principle, compare your data to predictions in a cross-multiplication table,
and use a model gene pool to examine the change in allele frequencies caused by harmful
genotypes in a given environment.
2 small bowls or cups
60 red beans
140 white beans
Draw a data table like the following:
Two red One red, one white Two white
Label one bowl or glass as "male gametes" and one as "female gametes." Count out 30 red beans
and 70 white beans and place them in one of the bowls. Mix the beans. Place another 30 red
beans and 70 white beans in the second bowl. Mix the beans. The red beans represent the
dominant allele for brown coat colour (B) in rabbits; the white beans represent the recessive
allele for white coat colour (b).
On another sheet of paper draw a cross-multiplication table. Complete the table to calculate the
expected frequency of red and white alleles in the population.
Without looking at the beans, reach into each bowl and draw out one bean.
Record what combination of beans you drew. After you record the result, place each bean back
in the bowl from which it came. Mix the beans.
Repeat another 49 times and record your results.
Suppose that homozygous dominant individuals cannot survive to reproduce. Look at your
data table to see how many homozygous dominant individuals you drew out. Remove one half
that number of red beans from each bowl. Each bowl now represents the gene pool of the
second generation. Draw another data table and label it "second generation" and repeat the
procedure of drawing beans 50 times.
1. What did each pair of beans you drew out of the bowls represent? (the genotype of one
offspring from the population)
2. How do the results of your first 50 draws compare with the frequencies predicted in your
1. What happened to the allele frequencies in the second generation when homozygous brown
rabbits were selected out of the population?