Download Gene Frequencies Lab

Evolution and Gene Frequencies:
A Game of Survival and Reproductive Success
Introduction:
Bengal tigers live high in the mountains of India where the temperature is very cold. The presence of fur (F) is
dominant to the absence of fur (f), which is recessive. Bengal tigers that inherit two dominant alleles (FF) or
one dominant and one recessive allele (Ff) have fur, while tigers that inherit two recessive alleles (ff) have no
fur. Because of this, the homozygous recessive trait is lethal. In this activity, you will examine natural
selection in a small population of wild Bengal tigers.
Purpose:
To determine the effect of random mating in a population of Bengal tigers possessing a recessive, lethal gene.
Procedure:
1. Complete the Title, Purpose, Hypothesis, and Materials sections on your paper.
2. Let one color of M&M’s represent the dominant allele (F) for fur and the other color of M&M’s
represent the recessive allele (f) for no fur in a Bengal tiger population.
3. Let the paper bag represent the deep dark jungles of India where random mating occurs unwitnessed by
Biology students.
4. Label one Petri dish as “F” for the dominant allele. Label a second Petri dish as “f” for the recessive
allele. Label the third Petri dish “RIP” for those that were not naturally selected to survive the cold
environment.
5. Place the 50 dominant-colored and 50 recessive-colored alleles (M&M’s) in the dark jungle bag and
shake up (mate) the tigers. DON’T LOOK!
6. Select two alleles at a time, and record in your chart next to generation #1 each tiger produced according
to the combination of alleles or genotype. (You can use tally marks to keep track.)
7. For each FF or Ff tiger produced, sort the dominant and recessive alleles into Petri dishes #1 and #2. All
homozygous recessive (ff) tiger cubs unfortunately get placed into Petri dish #3 or the RIP Graveyard.
Continue this procedure until all alleles have been sorted.
***Once in the RIP Graveyard, these alleles are no longer able to be passed on to the next generation and
become available to the sweet-toothed Homo sapiens. ENJOY!!
8. Count and record the number of “F” and “f” alleles into the chart. Total the number of “F” and “f”
alleles, and record into the chart.
9. Place the alleles of the surviving tigers (which have grown, survived, and reached reproductive age)
back into the dark jungle and mate them again to get the F2 generation.
10. Repeat steps 6, 7, 8, and 9 to obtain generations #2-10. Remember: all “ff” individuals become
part of the RIP Graveyard, and therefore cannot reproduce.
11. Determine the gene frequency of “F” and “f” for each generation and record in the chart. Express
your results in decimal form.
To determine the gene frequency, take:
• Number of “F” Alleles/Total Number of Alleles = Gene Frequency of “F”
• Number of “f” Alleles/Total Number of Alleles = Gene Frequency of “f”
(Tip: Gene Frequency of “F” + Gene Frequency of “f” = 1 for each generation.)
12. Record your group’s gene frequencies of “F” and “f” on the board.
13. Graph your data. Give a title for your graph. Label the x-axis as “Generation” and the y-axis as
the “Gene Frequency” in decimals. First, plot your own data using a solid line for “F” and a
dashed line for “f.” Then, plot the class data on the same graph using similar lines, but in a
different color. Make a key for your lines.
Evolution and Gene Frequencies: A Game of Survival and Reproductive Success
Title: ________________________________________________________________________________
Purpose: _____________________________________________________________________________
_____________________________________________________________________________________
Hypothesis: I predict that ________________________________________________________________
_____________________________________________________________________________________
Materials:
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Results: Data Table
Number of Number of Number of
Generation
FF
Ff
ff
Individuals Individuals Individuals
1
2
3
4
5
6
7
8
9
10
Number
of F
Alleles
Number
of f
Alleles
Total
Number
of
Alleles
Gene
Gene
Frequency Frequency
of F
of f
Results: Graph
Conclusion:
1. Do your results support your hypothesis? Explain why or why not.
2. What happened to the number of the dominant gene from one generation to the next? What happened to its frequency?
3. What happened to the number of the recessive gene from one generation to the next? What happened to its frequency?
4. What would happen to the gene frequency of the recessive allele if it became extinct?
5. In a real tiger habitat new animals often come into the habitat (immigrate), and others leave the area (emigrate). How
might immigration and emigration affect the gene frequency of “F” and “f” in this population of tigers? How might you
simulate this effect if you were to repeat this activity?
6. How might you simulate the effect of genetic drift or the founder’s effect if you were to repeat this activity?
7. How do your results compare with the class data? If significantly different, why are they different?
8. Define evolution. Are the results of this game/simulation an example of evolution?