Genetics of Drosophila Population Genetics and Chi Square Lab
Overview:
Fruit flies have been used in the field of genetics for years. Their simple genetics and 4 pairs of
chromosomes make them an ideal organism for genetic studies. The tiny little Drosophila
melanogaster has provided aspiring geneticists with over a century of interesting experimentation and
ground-breaking information. However, flies are very difficult to work with. So we are going to take
advantage of the benefits of the modern age and perform our fly lab in the virtual zone.
Directions:
1. Go to the following website: http://www.sciencecourseware.org/vcise/drosophila/
2. Create a new account using the class code: 12582955. (You could choose “enter as guest” but if
anything goes wrong or you do not have time to finish, none of your work will be saved and you will
have to start over.)
3. You will be performing four crosses:
Cross 1: Monohybrid -- wild type female x vestigial-winged male
Cross 2: Sex-linked? -- wild type male x white-eyed female
Cross 3: Dihybrid -- wild type female x vestigial, sepia-eyed male (female is wild type for both traits)
Cross 4: Linked genes? (Dihybrid) -- wild type female x purple-eyed, curved-winged male
(Note: The listed traits above are recessive – vestigial wings, white eyes, sepia eyes, purple eyes,
curved wings)
4. Follow the on-screen directions to choose the specified traits, order your flies, and perform the
cross. Record the data for the F1 generation in the virtual lab notebook. You should also record all
your data on the charts provided so you have a hard copy of the results.
5. Then you will need to cross the F1 flies to obtain F2 progeny. To do this, click on the piles of sorted
flies to zoom in. Then click the “Use in New Mating” button. Do this for both a male and a female.
Then return to your lab and click on the mating jar.
6. Sort your progeny and record the necessary data.
7. After you collect F2 data, clean out your incubator by clicking on the small trashcan next to it. This
resets your lab for the next cross.
8. Repeat the process (steps 4-7) for your other crosses. (Except Cross 2 only requires F1, no F2.)
9. When you have your data for all the crosses, write a null hypothesis for each cross and then apply
the Chi square analysis to the data to determine if you should accept or reject the null hypothesis.
Use the M&M handout to review Chi square. You can also use the Critical Values Chart from the
M&M lab or your AP Biology Formula Sheet to determine if you accept or reject your null hypothesis.