Genetic Variation & Allelic Frequency in Bunnies Lab

Introduction:

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.

In this activity, the dominant allele for normal fur is represented by F and the recessive allele for no fur is represented by f. Organisms have two alleles for every trait inherited.  Bunnies that inherit two F alleles or one F allele and one f allele have fur, while bunnies that inherit two f alleles have no fur.

 

Problem:  How does natural selection affect allelic frequency over several generations?

Procedure:

1. Based on the information in the introduction, write a hypothesis in the form of an If…then statement predicting which allele F or f will be more frequent in the population over ten generations.   

 

2. The kidney (red) beans represent the allele for fur (F), and the pinto (brown) beans represent the allele for no fur (f). The container represents the English countryside, where the rabbits randomly mate.

 

 3. There are three cups labeled.  One cup is labeled FF for the homozygous dominant genotype. The second cup is labeled Ff for the heterozygous genotype. The third cup is labeled ff for those rabbits with the homozygous recessive genotype.

 

4. From the center bowl, count out 50 red beans and 50 brown beans.

 

5. Place the 50 red and 50 brown beans (alleles) in the brown paper bag and shake up (mate) the rabbits.

 

 6. Without looking at the beans, select two beans at a time.  Record a tally on the separate tally chart for generation 1.  For instance, if you draw one red and one brown bean, place a tally in the chart under "Number of Ff individuals." Place the beans "rabbits" into the appropriate cup: FF, Ff, or ff.

 

7. Continue drawing pairs of beans and recording the tallies in the tally chart until all beans have been selected and sorted.

 

 

8.  Add up your tallies for each individual (FF, Ff, and ff) for generation 1.  Record these numbers in Data Table 1 on your answer sheet.  (Please note that the total number of individuals will be half the total number of beans because each rabbit requires two alleles.)

9. 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 container in the center bowl.  You will NOT be counting these beans because they represent bunnies that died.

10. Count the number of F alleles that were placed in both the FF cup and Ff cup in the first round.  Record the number of F alleles in Data Table 1 in the column labeled “Number of F Alleles”.

 

11. Count the number of f alleles that were placed in the Ff cup in the first round. Record the number of f alleles in Data Table 1 in the column labeled “Number of f Alleles”.

 

12.  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."

13. Determine the allelic frequency. To find the allelic frequency of F, divide the number of F alleles by the total number of alleles, and to find the allelic frequency of f, divide the number of f alleles by the total number of alleles. Express results as a percentage. Record the allelic frequencies for F and f in Data Table 1 in the columns labeled "Allelic Frequency F" and "Allelic Frequency f."  The sum of the frequency of F and f should equal one for each generation.

 

14.  Place the alleles of the surviving rabbits (which have grown, survived and reached reproductive age, FF and Ff) back into the brown paper bag and mate them again to get the second generation.

15. Repeat steps six through fourteen for generations two through ten. Make sure everyone in your group has a chance to either select the beans or record the results.

 

 16. Graph your frequencies. Prepare a LINE graph with the horizontal axis as the generation and the vertical axis as the allelic frequency in %. Plot all frequencies on one graph. Use two different colored lines for F and for f.   Draw BEST FIT lines. Make a color key and label your alleles.  Be sure to title the graph and label the axes. 

 

17. Complete the discussion questions.

 

 

 

Name ____________________________________________________ Period _________

 

Breeding Bunnies Data Collection & Analysis Worksheet

 

 

Hypothesis:

 

 

 

 

 

 

 

Data Table 1:

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

Allelic Frequency of F

Allelic Frequency of f

1

 

 

 

 

 

 

 

 

 

2

 

 

 

 

 

 

 

 

 

3

 

 

 

 

 

 

 

 

 

4

 

 

 

 

 

 

 

 

 

5

 

 

 

 

 

 

 

 

 

6

 

 

 

 

 

 

 

 

 

7

 

 

 

 

 

 

 

 

 

8

 

 

 

 

 

 

 

 

 

9

 

 

 

 

 

 

 

 

 

10

 

 

 

 

 

 

 

 

 

 

 

 

Analysis:

 

1.      Was your original hypothesis correct or incorrect? Give data from Data Table 1 to support this.

 

 

2.      What is happening to the number of alleles for the dominant characteristic?

 

 

3.      What is happening to the number of alleles for the recessive characteristic?

 

 

4.      How does the number of alleles for the dominant characteristic compare with the number of alleles for the recessive characteristic at the end of the lab? 

 

 

 

5.      What is happening to the frequency of the dominant allele during the lab?

 

 

6.      What is a happening to the frequency of the recessive allele during the lab?

 

 

 

7.      What does a change in allelic frequency indicate?

 

 

 

8.      In a real rabbit habitat new rabbits often come into the habitat (immigrate), and others leave the area (emigrate).  How might immigration of a bunch of bunnies with fur affect the allelic frequency of the F and the f allele in this population of rabbits? 

 

 

9.      How might immigration of a bunch of furless bunnies affect the allelic frequency of the F and the f allele in this population of rabbits? 

 

 

10.  How might you simulate the situation in question #8 if you were to repeat this activity?

 

 

11.  How might you simulate the situation in question #9 if you were to repeat this activity?

 

 

 

12.  How are the results of this simulation an example of evolution?

 

 

TALLY CHART FOR BREEDING BUNNIES

 

Generation

Number of FF individuals

Number of Ff individuals

Number of ff individuals

1

 

 

 

 

 

2

 

 

 

 

 

3

 

 

 

 

 

4

 

 

 

 

 

5

 

 

 

 

 

6

 

 

 

 

 

7

 

 

 

 

 

8

 

 

 

 

 

9

 

 

 

 

 

10