This week was the start of my rotation.  So far, I’ve been playing around with vials of fruit flies that are usually kept just beside the work desk.  Occasionally, lone flies that have escaped land on my laptop while I’m reading.  Funny to think how fruit flies are the kitchen scourge of the summer months, and here I am with my precious bottle trying to grow myself a colony.

Under the microscope, these critters are actually quite cute.  To discriminate between flies that we’ve genetically tweaked and those that are normal, we look at several physical markers.  Some will have red eyes, others white.  Curly wings or straight wings.  Long bodies or tubby bodies.  And even count the difference in the number of bristles next to the eye!  For my project, all the ones with red eyes and curly wings are expressing transgenes, or the genes that we have engineered .

To make specific mating crosses, I’ve learned how to sort out the virgin females.  We need to use virgins because the females that have already mated can store sperm inside their bodies to use overtime.  So to be sure that all the offspring are from a specific male, we separate out the virgins, which are fatter, whiter, and “shinier.”  I place these in vials with males from another strain, and after a day or two, I can see several eggs that have been deposited on the bottom.  And if I look again the next day, the whole culture is crawling with tiny little maggots that make my skin itch just by looking at them.  It’s pretty marvelous.

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Drosophila have a rich background in science.  They were first used by Seymour Benzer to study whether genes can influence behavior, a revolutionary idea at the time when most people thought that behavior was solely a product of our environment.  Using some elegantly designed tests, Benzer demonstrated that fruit flies exhibit simple and reproducible behaviors.  Phototaxis, for example, where flies are attracted to the brighter side of the test tube.  Time-keeping, or circadian rhythm, where flies emerge from their pupal cases (after metamorphosis) always at a particular time of the day.  And memory–flies can recognize an odor that had been paired with an electric shock.

For such a small critter, flies have an amazing repertoire of actions and responses to visual, gustatory, and olfactory stimuli (to say the very least).  But more importantly, Benzer demonstrated that mutants for these behaviors can be isolated and used to pinpoint specific genes that regulate these functions; thus, opening the field for the genetic dissection of behavior.

Another great advantage of the fly system is that the development of the neural system is stereotyped and uniform for every fly.  For example, in the larvae, there are four classes of sensory neurons that innervate the entire body wall.  Each class is characterized by the morphology (or appearance and shape) of the cell.  You can locate the same class of neurons in the same exact location in every single fly.  This makes it very easy to study what genes determine the development of these neurons.  For my rotation project, I will be looking at the interaction of these neurons and the surrounding glia (accessory cells that facilitate the development and function of the nervous system).

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And finally, just to geek out a little, the professor who runs my lab had actually came from the lab of Seymour Benzer during his postdoctoral training.  Which means (if I decide to stick with this fly lab) that I could be a “descendant” of Benzer!  I am a link in scientific history!

Apple and Lemon Cakes from Technicolor Kitchen