Back in my undergrad days and shortly after I got married, I took a genetics class. As a practical experiment, we did cross breeding experiments on fruit flies. These flies are categorized by many characterists with names like "Wild Type", "Vestigial Wings", "Bar Eye", etc.

These experiments were time consuming. First, we had to get some fresh flies. Growing flies was more difficult than you might imagine. We used small plastic tubes with some blue food substance at the bottom and a mesh netting inside. Contaimination could ruin the experiment, so it was a happy day when we looked in our tubes and found maggots.

Female fruit flies often mate within 12 hours of emerging from the pupa. Once they mate, they can store sperm for quite some time. That means we had to get them shortly after they emerge while they were still virgins so we could isolate them from the males. This required us to check our experiment several times a day to see if the flies had emerged. I used to joke with by bride that I was going to the campus to look for "Wild-type female virgins." She took it in stride.

Of course, in order to isolate the flies by sex, we had to learn how to tell the sexes apart. To do that, we'd knock the flies out with ether or something similar (I did this almost 20 years ago so some of the memories have mercifully faded). Once they were out, we'd remove the flies from their container and examine their rear end using a dissecting scope. We learned how to tell the sexes apart and we'd isolate the females into a separate container. Once isolated, we could conduct controlled breeding experiments to determine the rates particular versions occurred in the population.

We actually went through several generations with the experiment. In all, I bred over 10,000 flies and manually categorized them by category and sex, then computed the statistics and checked them against the predicted results. Our results matched Mendel's predictions quite well, but I've hated flies with a passion ever since that class.