Breeding Bunnies

(A modification of Breeding Bunnies from the PBS website for Evolution  ©2001 WGBH Educational Foundation and Clear Blue Sky Productions, Inc. All rights reserved.)

 

          In this activity, you will examine natural selection in a small population of wild rabbits. Evolution, on a genetic level, is a change in the frequency of alleles in a population over a period of time. 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 (naked bunnies). This trait was first discovered in England by W.E. Castle in 1933. The furless rabbit is rarely found in the wild because the cold English winters are a definite selective force against it.

 

Note: In this lab, the dominant allele for normal fur is represented by F and the recessive allele for no fur is represented by f. Bunnies that inherit two F alleles or one F and one f allele have fur, while bunnies that inherit two f alleles have no fur. The red beans represent the allele for fur (F), and the white beans represent the allele for no fur (f). The container represents the English countryside, where the rabbits randomly mate.

 

Procedure:

1)      Create a table to record the numbers of individuals with each genotype (FF, Ff and ff), the numbers of each allele (F and f), the number of total alleles (F + f), and the gene frequencies for each allele (F and f) for all 10 generations (see below)

2)    Label one dish “FF” for the homozygous dominant genotype, a second dish “Ff” for the heterozygous genotype, and a third dish “ff” for the homozygous recessive genotype.

3)    Place 50 red beans and 50 white beans into the container

a.      Please note that frequencies have been chosen arbitrarily for this activity.

4)    Shake up (mate) the rabbits.

5)    Without looking at the beans, select two at a time, place them in the appropriate dish, and record the results on the data form next to "Generation 1."

a.      For example, if you draw one red and one white bean, place them in the dish labeled “Ff” and place a mark in the chart under "Number of Ff individuals."

6)    Continue drawing pairs of beans, sorting, and recording the results until all beans have been selected and sorted.

a.      Please note that the total number of individuals will be half the total number of beans because each rabbit requires two alleles.

7)    The “ff” 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 “ff” dish aside before beginning the next round.

8)    Count the F and f alleles (beans) that were placed in each of the "furred rabbit" dishes in the first round and record the number in the chart in the columns labeled "Number of F Alleles" and "Number of f Alleles."

a.      Note: You are counting each bean, but don't count the alleles of the ff bunnies because they are dead.

9)    Total the number of F alleles and f alleles for the first generation and record this number in the column labeled "Total Number of Alleles."

10) Place the alleles of the surviving rabbits (which have grown, survived and reached reproductive age) back into the container and “mate” (shake) them again to get the next generation.

11)  Repeat steps five through ten to obtain generations two through ten. If working as a team, make sure everyone in your group has a chance to either select the beans or record the results.

12) Determine the gene frequency of each allele (F and f) for each generation by dividing the number of each allele by the total number of alleles. Express results in decimal form and record this information in the chart columns labeled "Gene Frequency F" and "Gene Frequency f."

a.      For example, to find the gene frequency of F for generation 1, divide the number of F alleles for generation 1 by the total number of alleles for generation 1.

b.     The sum of the frequency of F and f should equal one for each generation.

13)  Give your findings to your teacher to record the class results.

Generation

Number of FF individuals

Number of Ff individuals

Number of ff individuals

Number of F alleles

Number of f alleles

Total number of alleles

Gene frequency of F

Gene frequency of f

1

 

 

 

 

 

 

 

 

2

 

 

 

 

 

 

 

 

3

 

 

 

 

 

 

 

 

4

 

 

 

 

 

 

 

 

5

 

 

 

 

 

 

 

 

6

 

 

 

 

 

 

 

 

7

 

 

 

 

 

 

 

 

8

 

 

 

 

 

 

 

 

9

 

 

 

 

 

 

 

 

10

 

 

 

 

 

 

 

 

 

Observations

  1. USING EXCEL- Make a graph showing the relationship of each generation to the frequencies of each allele for your data. Make two separate lines, one for the frequency of F and the other for the frequency of f.
  2. USING EXCEL- Make a graph showing the relationship of each generation to the frequencies of each allele for the class data. Make two separate lines, one for the frequency of F and the other for the frequency of f.
  3. Using your data, compare the number of alleles for the dominant characteristic with the number of alleles for the recessive characteristic for generation 10.
  4. Using your data, compare the frequencies of the dominant allele to the frequencies of the recessive allele for generation 10.

 

Conclusions

  1. How do your results compare with the class data? If significantly different, why are results different?
  2. 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 F and f in this population of rabbits?
  3. How might you simulate the effect of immigration and emigration if you were to repeat this activity?
  4. How are the results of this simulation an example of evolution?

 

EXTRA CREDIT: 5pts

          Using your data and the Hardy-Weinberg Variables and Equations (see below) to solve the following questions.

 

  1. In generation 1, what was the frequency of homozygous recessive individuals? heterozygous individuals? homozygous dominant individuals? (SHOW WORK)
  2. For generation 1, do the frequencies of homozygous recessive, heterozygous and homozygous dominant individuals equal 1 as expected according to the final Hardy-Weinberg equation? (SHOW WORK)
  3. In generation 5, what was the frequency of homozygous recessive individuals? heterozygous individuals? homozygous dominant individuals? (SHOW WORK)
  4. For generation 5, do the frequencies of homozygous recessive, heterozygous and homozygous dominant individuals equal 1 as expected according to the final Hardy-Weinberg equation? (SHOW WORK)
  5. In generation 10, what was the frequency of homozygous recessive individuals? heterozygous individuals? homozygous dominant individuals? (SHOW WORK)
  6. For generation 10, do the frequencies of homozygous recessive, heterozygous and homozygous dominant individuals equal 1 as expected according to the final Hardy-Weinberg equation? (SHOW WORK)

 

Hardy Weinberg Variables and Equations

p=frequency of dominant allele

q= frequency of recessive allele

                   p + q = 1

p2= frequency of individuals who are homozygous dominant

q2= frequency of individuals who are homozygous recessive

2pq= frequency of individuals who are heterozygous

                   p2 + 2pq + q2 = 1