Breeding Bunnies
(adapted from NOVA:Evolution)
You will examine natural selection and genetic drift in a small population of wild rabbits. Breeders of rabbits
have long been familiar with a variety of genetic traits that affect the survivability of rabbits in the wild, as well
as in breeding populations. One such trait is the trait for furless rabbits. This trait was first discovered in
England by W.E. Castle in 1933.
Note: For this activity the dominant allele for normal fur is represented by G (black beans) and the recessive
allele for no fur is represented by g (white beans). The container represents the English countryside, where
the rabbits randomly mate.
Hypothesis: In your Biology Journal record your hypothesis for how natural selection affects gene frequency
over several generations.
Prediction: State what you would predict (if your hypothesis is supported) about the frequency of G alleles
and g alleles in the population of rabbits after 10 generations, where gg bunnies are selected against (do not
survive).
Materials:
 50 black beans
 50 white beans
 1 bag



Graph paper
Writing utensil
4 cups labeled GG, Gg, gg, and dead bunny
Procedures:
1. Place the 50 black and 50 white beans (alleles) in the bag and shake up (mate) the rabbits.
2. Randomly select two at a time, and record the results on the data form next to "Generation 1." For
instance, if you draw one black and one white bean, place a mark in the data table under "# of Gg
individuals." Continue drawing pairs of beans and recording the results in your chart until all beans
have been selected and sorted. Place the "rabbits" into the appropriate cup: GG, Gg, or gg. (Please note
that the total number of individuals will be half the total number of beans because each rabbit requires two alleles.)
3. The gg bunnies are born furless. The cold weather kills them before they reach reproductive age, so
they can't pass on their genes. Place the beans from the gg cup into the “dead bunny” cup before
beginning the next round.
4. Place the alleles of the surviving rabbits back into the bag and mate them again to get the next
generation.
5. Repeat steps two through three to obtain generations two through ten.
Analysis:
6. Calculate the G and g alleles by looking at the number of G alleles in each individual. For example, if
you have 15 individuals with GG genotype, then there are 30 G alleles (2 x 15). If you have 20
individuals with Gg genotype, then there are 20 G alleles. Add them together to get the total for that
generation.
7. Determine the gene frequency of G and g for each generation and record them in the chart in the
columns labeled "Gene Frequency G" and "Gene Frequency g."
Frequency of G = G/total # of alleles
8. Plot your frequencies on a graph.
Frequency of g = g/total # of alleles
The sum of the frequencies should = 1
Analysis Questions:
1. Was your original hypothesis supported by the data? Explain.
2. How does the number and frequency of alleles for the dominant characteristic compare with the
number of alleles for the recessive characteristic? Frequency of G allele increases over time, while the
frequency of g allele decreases.
3. The change in the frequency of alleles is called genetic drift. Why is genetic drift more likely to occur in
smaller populations? Because genetic variation is lowered in smaller populations.
4. Why does genetic drift occur in the first place? Some individuals may, just by chance, leave behind a
few more (or less!) descendants than other individuals. The genes of the next generation will be the
genes of the "lucky" individuals, not necessarily the healthier or "better" individuals. That, in a
nutshell, is genetic drift. It happens to ALL populations — there's no avoiding the vagaries of chance.
5. In a real rabbit habitat new animals often come into the habitat (immigrate), and others leave the area
(emigrate). How might emigration and immigration affect the gene frequency of G and g in this
population of rabbits? Immigration might make drift happen at a slower pace if you add more
variation to the population. Emigration will have little effect unless the migrants are genetically
different from the population.
6. How could you simulate migration if you were to repeat this activity? Randomly add or take away
beans or corn to the bag periodically.
7. How do your results compare with the class data? If significantly different, why are they different?
8. How are the results of this simulation an example of evolution? The frequency of alleles in the
population changed over time.
9. What are the key components of natural selection? 1) Overproduction 2) heritability 3) struggle to
survive, 4) some individuals are better suite (adaptation)
10. What kinds of limited resources can create a struggle between individuals in a population? Food,
space, mates
11. What kinds of variable traits (other than fur or lack of) within a population might natural selection act
upon? Fur color, size, ability to attract mates
12. How does natural selection affect the genetic variation within the next generation of the same
population? it decreases and can eventually lead to speciation
Table 1. Data Table for Breeding Bunnies Investigation
Generation
# of GG
individuals
# of Gg
individuals
# of gg
individuals
# of G
alleles
# of g
alleles
Frequency
of G
Frequency
of g
1
2
3
4
5
6
7
8
9
10
4
5
6
7
8
9
10
4
5
6
7
8
9
10
Table 2. Data Table for Breeding Bunnies Investigation
Generation
# of GG
individuals
# of Gg
individuals
# of gg
individuals
# of G
alleles
# of g
alleles
Frequency
of G
Frequency
of g
1
2
3
Table 3. Data Table for Breeding Bunnies Investigation
Generation
# of GG
individuals
# of Gg
individuals
# of gg
individuals
# of G
alleles
# of g
alleles
Frequency
of G
Frequency
of g
1
2
3
Analysis Answers:
1. Was your original hypothesis supported by the data? Explain.
2. How does the number and frequency of alleles for the dominant characteristic compare with the
number of alleles for the recessive characteristic? Frequency of G allele increases over time, while the
frequency of g allele decreases.
3. The change in the frequency of alleles is called genetic drift. Why is genetic drift more likely to occur in
smaller populations? Because genetic variation is lowered in smaller populations.
4. Why does genetic drift occur in the first place? Some individuals may, just by chance, leave behind a
few more (or less!) descendants than other individuals. The genes of the next generation will be the
genes of the "lucky" individuals, not necessarily the healthier or "better" individuals. That, in a
nutshell, is genetic drift. It happens to ALL populations — there's no avoiding the vagaries of chance.
5. In a real rabbit habitat new animals often come into the habitat (immigrate), and others leave the area
(emigrate). How might emigration and immigration affect the gene frequency of G and g in this
population of rabbits? Immigration might make drift happen at a slower pace if you add more
variation to the population. Emigration will have little effect unless the migrants are genetically
different from the population.
6. How could you simulate migration if you were to repeat this activity? Randomly add or take away
beans or corn to the bag periodically.
7. How do your results compare with the class data? If significantly different, why are they different?
8. How are the results of this simulation an example of evolution? The frequency of alleles in the
population changed over time.
9. What are the key components of natural selection? 1) Overproduction 2) heritability 3) struggle to
survive, 4) some individuals are better suite (adaptation)
10. What kinds of limited resources can create a struggle between individuals in a population? Food,
space, mates
11. What kinds of variable traits (other than fur or lack of) within a population might natural selection act
upon? Fur color, size, ability to attract mates
12. How does natural selection affect the genetic variation within the next generation of the same
population? it decreases and can eventually lead to speciation