Koala Killer Allele Directions

 

In this lab, you will be working with a population of Koala’s living in a forest in Australia.  The koalas’ primary food source is eucalyptus leaves.  The allele for having claws (N) is dominant to the allele for being clawless (n).  Because of this, the homozygous recessive individual (nn) will have NO claws and thus NO chance for survival.

 

For our simulation:

        Paper bag = gene pool of the koala population

        White bean = normal allele (N) for claws

        Yellow bean = defective allele (n) for clawless

        2 beans drawn = the genotype of one koala bear

 

PROCEDURE:

  1. Obtain a gene pool containing 50 normal alleles (N) and 50 defective alleles (n).
  2. Record and calculate the initial allele frequencies on your data chart. Write a hypothesis above the data table which predicts what will happen to the frequency of the defective allele over four generations in the eucalyptus forests of Australia.
  3. Label one Petri dish “N”, and one Petri dish “n”.  Label the third Petri dish “graveyard”.
  4. Shake the bag containing all the alleles in order to “mate” the koalas in the population.
  5. Blindly select two alleles at a time and record the genotype (as a tally) of the newborn koala on your data chart under “NN”, “Nn” or “nn”.
  6. If the koala born has no claws (nn), put both alleles in the graveyard.  This koala has died (R.I.P.) and THESE ALLELES (beans) WILL NOT BE COUNTED NOR USED AGAIN!
  7. If the koala born has claws, sort the dominant (N) and recessive (n) alleles into the correct petri dishes.
  8. Continue to draw out alleles (and tally genotypes) until all the koalas (two beans each) in the bag have been “born”.
  9. Count and record the total number of “N” and “n” alleles obtained and record in chart.  Do NOT count the alleles in the graveyard.  These koalas are dead and will not be passing their genes or alleles on.  Calculate the new gene frequency for the remaining population.  Remember to divide by the NEW TOTAL of remaining alleles. (example- # of “n” alleles/ total # of remaining alleles)
  10. Once counted, place all the alleles from the surviving koalas back into the gene pool.  DO NOT INCLUDE THE ALLELES FROM THE GRAVEYARD!  The gene pool will be shrinking during this activity.
  11. Repeat steps 4-10 three MORE times until a fourth generation has been born and counted.
  12. Obtain class averages for the frequencies of “N” and “n”.