Our Apologia Biology text didn’t have any actual genetics experiments for Module 8, so I decided to add one. The students will be breeding and studying fruit flies (drosophila) for the next month to reinforce their study of genetics.
The flies that I ordered (and yes, the students were astounded that I actually paid for fruit flies!) were of two types: wild (winged) and apterous (wingless). Both types had sex-linked traits of yellow bodies and red eyes for females and gray bodies with white eyes for males. We won’t be going into much discussion of the principles of sex-linked traits, but these features will make it much easier to differentiate males and females.
On week one, the students read parts of the Carolina Drosophila manual and filled out some worksheets on the characteristics of drosophila and made predictions about the resulting F1 and F2 crosses if the wild trait were dominant and if the apterous trait were dominant. I didn’t tell them which was dominant—they will have to figure that out for themselves.
Next, we examined the flies with magnifying glasses and identified the traits we were looking for—winged vs. wingless, eye color, and body color. We also observed the larvae and pupae in the vials. I had discarded the adult flies the previous day, to ensure that we were only dealing with young, virgin flies.
Then they separated the flies of each type into male and female and started the F1 crosses by putting several wild males with several apterous females in one vial and several wild females with apterous males in the other vial. We did have a small problem in that only about 6-8 new adult flies had appeared since I cleared the vials, so Emily and I had to add new adult flies over the 2 days following our lab day.
For the remainder of our lab class, we did some chapter review. Then we worked together to create a Punnett Square for a dihybrid cross of a green legged, diamond backed turtle (dominant traits) with a yellow-legged square patterned back turtle (recessive traits). The students made up our fictional turtle characteristics—no resemblance to real life!
In two weeks, after the F1 generation of fruit flies hatches, we will start the F2 generation.