FALCONIUM

In theory, or perhaps romanticized legend, the AP Biology fruit fly lab is a fun opportunity for students to adopt flies, affectionately name their new foster pets (often after friends), watch them grow and, when the time is right, examine them under a microscope to note their phenotypes. However, romanticized legend has also left out some significant unsavory details, such as the disobedience of the flies, which must be dealt with in reality. Despite the frustrations of working with skittish flies, the fly lab was still ultimately an interesting and useful experience that students planning to take AP Biology can look forward to in a year's time.

We began by preparing vials of sticky food that also served as homes for our flies. Our adopted fly pets were the F1 generation, the offspring of genetically prepared parents; this was to maintain control over the phenotypes that would appear in the experiment so that the modes of inheritance for traits could be easily determined. Like many others, my lab partner and I decided to name our flies after friends and certain cartoon characters. Unfortunately, we did not get to see our dear pets very often. They remained in their vials with their pupa and larvae siblings, eating the nutritional concoction we had prepared for them earlier.

Finally, the day came when we got out the light microscopes, paintbrushes, Q-tips, petri dishes, and fly nap. We put our flies to sleep with the fly nap, then carefully poured them onto the petri dish, using paintbrushes to dust off flies stuck to the sides of the vial or to the food. The flies, like stubborn toddlers, sometimes refused to fall asleep, and feebly crawled along the side of the vial or buzzed around frantically until the chemical finally overpowered them. Most people were forced to use liberal amounts of fly nap to coerce their flies into slumber. As a result, the whole classroom was pervaded with the stench of fly nap before long, and became so on every lab day.

We then placed our fly-filled petri dish underneath the microscope, and began noting our flies' traits: gender, eye shape (round, dimple, or bar), eye color (red or white) and wing length (long or vestigial). Sadly, this was harder in practice than it sounds listed in a magazine. Many flies were positioned inconveniently, or had had their wings and appendages damaged in the transfer to the petri dish. My lab partner and I had to examine the plate of flies three times before we got phenotype results that made sense. The flies did not help by waking and moving around after fifteen to twenty minutes, requiring more fly nap. Still, some flies were unaffected and spun in circles or jogged around the dish instead of falling back asleep, making it difficult for us to keep track of flies we had already observed.

Eventually, the class was able to pool its F1 observations and make hypotheses on the mode of inheritance for each trait. Eye color and shape were thought to be sex-linked, and wing shape autosomal, with vestigial wings, round eyes, and white eyes as recessive phenotypes. From these hypotheses, we were able to predict F2 generation results. A few days later, we transferred our flies from our first vial to a new vial to prevent flies of different generations from mating and invalidating the results. This was done via pouring, without fly nap. Consequently, many people inadvertently liberated their flies or killed them when attempting to pour them into the new vial. Then, the scenario of fly examining with fly nap was repeated once more with the F2 generation.

After pooling our F2 results, we compared them with our hypotheses ratios and statistically analyzed them using a technique called chi square. Through chi square, we determined with a series of simple calculations whether the observed deviations from our hypotheses ratios were statistically significant.

That was the last we saw of our flies. The remainder of the fly lab period was spent on calculations and discussions of chi square results. Despite the trouble the flies had given us and the memories of fly nap, parting was sorrowful, for we knew the flies would be euthanized soon after. We are, and always will be, greatly thankful to the flies and (of course) our biology teachers for allowing us to observe modes of inheritance hands-on in the classroom with the fruit fly lab.