Evolution and Gene Frequencies:
A Game of Survival and Reproductive Success
1994 Woodrow Wilson Biology Institute
In this population of Bengal tigers, alleles exist as either dominant
or recessive. Bengal tigers live high in the mountains of India
where the temperature is very cold. The presence of fur is dominant
to the absence of fur, which is recessive. Because of this, the
homozygous recessive trait is lethal.
To determine the effect of random mating in a population of tigers
possessing a recessive gene.
State a hypothesis to predict what will happen to the lethal recessive
gene after 10 generations in a closed population.
- 50 red M & M candies
- 50 green M & M candies
- 1 paper bag
- 3 Petri dishes
- A student with a sweet tooth
- Let 50 M & M's represent the allelle for fur and
50 M & M's represent the allele for no fur in a Bengal
- Let the paper bag represent the deep dark jungles of India
where random mating occurs unwitnessed by biology students.
- Label one Petri dish 'H' for the dominant allele.
Label a second Petri dish 'h' for the recessive allele.
Label the third Petri dish 'RIP' for those were
not naturally selected to survive the cold environment.
- Place the 50 red and 50 green alleles (M & M's)
in the dark jungle bag and shake up (mate) the tigers. DON'T
- Select two alleles at a time and record in your chart next
to generation #1 each individual (combination of alleles or genotype)
tiger produced. Sort the dominant and recessive alleles resulting
from HH an Hh genotypes into Petri dishes #1 and #2. All homozygous
recessive tiger cubs unfortunately get placed in dish #3 ó
the RIP Graveyard. Continue this procedure until all alleles have
been counted and 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!!
- Count and record the 'H' and 'h'
alleles obtained and place in the chart. Total the number of 'H'
an 'h' for the first generation and record this number
- 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.
- Repeat steps 5,6, and 7 to obtain generations #2 - 10. Remember:
all 'hh' individuals become part of the RIP Graveyard
and therefore cannot reproduce.
- Determine the gene frequency of 'H' and 'h'
for each generation and record in the chart.
To determine the gene frequency take:
# of 'H'/Total = Gene frequency of 'H'
(Express as a decimal)
# of 'h'/Total = Gene frequency of 'h'
The frequency of 'H' and 'h' = 1 (all the alleles for fur in the population)
- Plot your frequency of 'H' and 'h'
on one graph using a solid line for 'H' and a dotted
line for 'h'. Plot the class data on the same graph
using the same symbols but a different color.
Explain your answer.
- Do your results support your hypothesis? If not, explain why.
- What happened to the number of the dominant gene from one generation
to the next?
What happened to its frequency?
Account for any change.
- What happened to the number of the recessive gene from one
generation to the next?
What happened to its frequency?
Account for any changes from generation to generation.
- What would happen to the gene frequency of the recessive allele
if it became extinct?
- How would emigration and immigration affect the gene frequency
of 'H' and 'h' in this population of
- Compare your data with the class data which will be recorded
on the blackboard.
- Define evolution. Are the results of this game/simulation an
example of evolution?
Name_________________________ Date______________ Section___________________
Evolution And Gene Frequencies Game/Simulation
Name of Gene____________________in _______________
Describe natural selective pressures on:
|Number of Individuals
|Number of Genes
Now set up a graph of Evolution. Label the y-axis, Allele Frequency
and the X-axis, Generations. You may use any graphing program
available on the computer or simply do your graph by hand.
The Woodrow Wilson National Fellowship Foundation
CN 5281, Princeton NJ 08543-5281