Life cycle of…(part 2)

OK, so I’ve tattled on both my kids this week–Camilla and her puff ball pet and Robin with his stuck finger misadventure. It’s time to tattle on myself and on my husband, who wasn’t my husband yet at the time of this story.

Waaaay back in 1994 we were high schoolers who liked to make eyes at each other through lab goggles.

cartoon drawing of owl with goggles and lab coat

by pugg71 on Flikr

We did a science project together, investigating whether fruit flies’ recessive trait of white eyes (versus the usual red, or wild type eyes) would occur more often than expected when the flies were exposed to ultraviolet light.

On paper we could work Punnet squares through several generations’ worth of pea plants, or flies, or whatever, to figure out what percentage of the nth generation would have the trait in question.

Punnet square showing yellow and green peas hybidization

By Pbroks13, available under CC-BY-SA-3.0 license, via Wikimedia Commons

So, why not move up to Drosophila melanogaster?

fruit fly red eyes

By André Karwath, licensed under the Creative Commons Attribution-Share Alike 2.5 Generic license, via Wikimedia Commons

(Feeling rusty on your high school bio? Click here and scroll down for an explanation of the sex-linked trait of white eyes in fruit flies, using Punnet squares.)

Why zap the flies with UV rays? Because if UV rays can cause mutations in fruit flies at a rate higher than normal genetic variation would predict, well, then, that’s just one more bit of evidence to add to the argument that UV rays are bad for humans and cause cancer and wrinkles.

Went the logic.

I don’t remember whether the literature we reviewed actually mentioned anything about UV effects on fruit fly mutations or linking studies with UV and fruit flies to humans. But the high school brain makes leaps.

And, a UV lamp was easy to get a hold of. It created a condition we could measure.

If only we’d known about D. melanogaster’s penchant for beer. Now THAT would have been fun to tinker with, though I can’t imagine getting away with it.

The day the larvae arrived in their vials with their blue medium, my mom banished the project to the basement and threatened to make us relocate if she found any flies wandering out of bounds. Heretofore we had spent a lot of time just laughing over all the odd mutations other scientists had found within the 4-chromosome fruit fly genome.

For instance, a gene that instructs cells that would normally become antennae to become legs instead. Flies with no eyes. Curly wings. Getting stuck while copulating!

We should have bought a real anesthetic for knocking out the little banana-eaters when we wanted to study them, but instead we put their vials on ice until movement inside slowed. Then we’d tap them out of the vials onto petri dishes and turn them over on their backs so we could count how many males and females. We’d also count how many were red-eyed and how many white.

Image from Carolina Biological Supply website

After a few minutes the icy water we were floating the petri dishes on would warm up enough that the flies began staggering around. We’d herd them back in their vials before they could take wing.

The week after Christmas my lab partner went on a trip to Florida, leaving me with one of the big data collections. Which generation we were on again?

We turned in some sort of write up but by the time the science fair came, we were out of time to make a poster and I don’t think we ever determined the effects of the UV rays. But, we’d learned how to recognize and chart genetic mutations and how to handle living subjects (sort of; a few did find their way into the kitchen).

And, we’d learned some fun facts in the literature and grasped the overall concept of genetics a little more firmly than we would have done otherwise.

In the end I think we just released the bugs outside.

4 thoughts on “Life cycle of…(part 2)

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