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Cross Out the Mutation!

You get to be a mutated fruit fly for the day. Your goal is to cross with other fruit flies in your class in order to create wildtype, or normal, flies. Read the procedure and answer the pre-lab questions before beginning.

Procedure

· Your teacher will assign you to be an eyeless or curly winged fruit fly.

· If you are eyeless you must wear a blindfold; if you are Curly you must hop to get around the classroom.

· Pick a classmate to cross with and fill out the first cross on the third page. You need to make two Punnett squares for the two mutant genes. The “+” is the wildtype version of the gene, the “Cy” is the Curly gene, and the “ey” is the eyeless gene.

· For the eyeless cross your genotype is “ey/ey” if you have the recessive eyeless mutation and “+/+” if you have the Curly mutation (and therefore don’t have the eyeless mutation). For the Curly cross your genotype is “Cy/+” if you have the dominant Curly mutation and “+/+” if you have the eyeless mutation (and therefore don’t have the Curly mutation). Here is an example of a cross:

Recessive Eyeless Dominant Curly

· For both the Curly and eyeless crosses, flip a coin with your partner to see who gets to pick their genotype first. For example, for the Punnett squares above, both partners would be ey/+ but one will be Cy/+ and the other will be +/+. If you have the eyeless phenotype put the blindfold on, if you are Curly start hopping, and if you are wildtype you can walk normally. Remember, Curly is dominant and eyeless is recessive so if your genotype is Cy/+ you have to hop but if your genotype is ey/+ then you do not have to wear the blindfold.

· With your new genotype and phenotype, pick a classmate to do another cross with. Repeat this for four crosses. Remember, your goal is to be a wildtype fruit fly.

Prelab Questions

What strategies do you plan to use to make wildtype flies?

What percentage of the class do you anticipate will be wildtype at the end? Eyeless? Curly?

Cross 1:

Your phenotype: ___________________

Your genotype: ____/____, ____/____

Your mate’s phenotype:___________________

Your mate’s genotype: ____/____, ____/____

Your new genotype: ____/____, ____/____

Your new phenotype:___________________

Cross 2:

Your mate’s phenotype:___________________

Your mate’s genotype: ____/____, ____/____

Your new genotype: ____/____, ____/____

Your new phenotype:___________________

Cross 3:

Your mate’s phenotype:___________________

Your mate’s genotype: ____/____, ____/____

Your new genotype: ____/____, ____/____

Your new phenotype:___________________

Cross 4:

Your mate’s phenotype:___________________

Your mate’s genotype: ____/____, ____/____

Your new genotype: ____/____, ____/____

Your new phenotype:___________________

Results and Analysis

What percentage of the class had each genotype and phenotype at the end? How does this compare with your prediction?

What was the best strategy for making wildtype flies?

What did you learn from this activity?