Have any of you participated in or led the genetics lab using fruit flies?
May 19, 2012 12:01 PM   Subscribe

Have any of you participated in or led the genetics lab using fruit flies?

I am teaching an intro to genetics class to gifted 4-6th graders this summer and am planning to do the standard Drosophila genetics lab with my group. I am not a science teacher, so I have not done this lab before. Because the class is only 2 weeks long, I will have to get it setup and going for them to observe the second generation. I think I am okay on the basic concepts covered in the lab, but I am looking for pointers in how you actually bred the flies from a culture, as I am having trouble finding specific instructions online.
posted by shrimpsmalls to Education (12 answers total) 1 user marked this as a favorite
I did a similar fruit fly experiment as a student my senior year in high school. I don't remember most of the details about how we mixed the food solution, or administered the anesthetic to study the flies, or really anything about the experiment at all, but I can tell you: we were absolutely terrible at it. We could not administer the anesthetic properly for the life of us, so we killed most of our flies and horribly mutated the others. When we picked up flies to look at them under the microscope for whatever it was we were looking for (eye color?), we accidentally stabbed and crushed a ton, and when we did manage to get one under the microscope we were horrified at all the mutations we had accidentally caused -- no eyes at all, far too many wings, legs growing out of the mouth, antennas in place of eyes, everything. I think we ended up fabricating all of our numbers just so we wouldn't have to keep killing more flies. My lab partner and I are still friends, and 8 years later we still talk about the holocaust we accidentally perpetrated on our subjects.

Which is to say: two relatively smart high school seniors, putting forth as much effort as we could muster the month before graduation, had lots of trouble performing this experiment. Others in the class might have had better success, I don't remember (they probably did; neither my partner nor I were particularly science-y). Even if you're doing the breeding yourself, don't be surprised if some of your students really struggle with something as simple as transferring the fly to the microscope. It might also be worth preparing them for potential mutations. It sounds completely ridiculous and I'm a little embarrassed about it, but I still feel absolutely awful that I probably inflicted terrible suffering upon those poor little flies. The memory of finding flies with legs instead of mouths is a very vivid one for me.
posted by lilac girl at 12:46 PM on May 19, 2012 [2 favorites]

I did this lab in high school, lo these many decades ago. The students worked independently, IIRC, and I still recall that my mutations were Vermillion (eyes) and Vestigial (wings). (Some of the students only did a single mutation.)

I don't recall having any particular problems. Anesthetize with ether in a little plastic vial, sex the pupae by the black combs on the forelegs, keep the boy flies apart from the girl flies until you want to cross them, then wait through 2-3 generations to see the mutations disappear, then reappear in 1:2:1 (or maybe 1:2:4:2:1?) ratios. I'm pretty sure I didn't have to make up my data, either; it just came out pretty close to right.

You'll want to have a nice binocular dissecting 'scope and a fair bit of practice using it. Maybe you can enlist one of your students to help with the setup work. I bet s/he'd learn plenty!
posted by spacewrench at 1:12 PM on May 19, 2012

I am looking for pointers in how you actually bred the flies from a culture...

Oops, I see that I failed to answer your question. Forgive me.

I don't remember (or never knew) how my teacher received the flies we worked with. However, I do remember mixing a grain-based (and blue-dyed) food substance, and putting it into clear plastic tubes where the flies were bred. We also had sheets of coarse white plastic mesh that were inserted over the food, on which the flies would walk around and lay eggs. The tubes were capped with foam-rubber plugs.

For breeding, I think (but am not 100% sure) that I took pupae from purebred vials of each mutation, sexed them, and put M-Vg + F-Vm (and/or vice-versa) into fresh tubes. The pupae hatched shortly thereafter, shagged and laid new eggs. Those hatched, grew up in the food mush, and eventually wriggled up onto the mesh, where I was able to pull them out, sex them, and put them in second-generation tubes.

IIRC, the thing that we were warned about most vigorously was not mis-sexing the pupae so as to have the possibility of M-F pairs with the same mutation. I can't remember whether the mutations were sex-linked, or that sex was merely a convenient method for separating carriers of each genotype.
posted by spacewrench at 1:44 PM on May 19, 2012

Hi. I work with Drosophila, and top Drosophila scientists, including the guy who started this place and this place. I say this with respect, but I think that you may be reaching way, way too high here, especially for working with 4th-6th graders - even gifted ones. The complexity of the information, combined with the required technical know-how, makes this very difficult. I did this lab with college students in an intro class, and a lot of them had a very, very difficult time with it.

Here's an overview of fly husbandry that may answer some of your questions.

These are the three things that I would be most concerned about with your planned lesson:

1. Do you have CO2 lines set up in your lab space, connected to your microscopes, or will you need to use an anaesthetic to examine the flies? Neither ether nor flynap is remotely safe enough to let children of this age handle.

2. Learning to sex flies (not pupa, but young flies) is required for getting good crosses - you'll have to collect virgin females (i.e., >8 hours post eclosure) in order to do crosses that demonstrate independent assortment of chromosomes. If you haven't done this before, you'll need to start practicing now. I really don't think 10 year olds are going to be able to do this.

3. Also, the generation time of fruitflies is 2 weeks, assuming you have access to the proper incubators. If not, it'll be much longer.

If you really want to use flies to do a genetics lesson, I would recommend that you set up all of the crosses, and do it as a demonstration. Here's how I would suggest you do that: do all of the crosses yourself, ahead of time, so that you can show the kids the G0, F1 and F2 generations all on the same day (have them set up on different scopes, ready for the kids to look/score/count/do whatever you want to do). Start about 8 weeks before you want to do the demonstration. You could even do the crosses, freeze the flies, and then have the students look at each generation/count, without having to worry about anaesthetics.

lilac girl, please let yourself off the hook about those flies you worked with! It's extremely unlikely to the point of impossibility that your ether overuse caused those mutations. Far more likely, you were working with characterized mutants like antennapedia (sp?), which is, in fact, a mutation in which flies grow legs instead of antennae) - at most, you combined a few known mutations from different parental stocks. Your teacher probably gave you a guilt trip to try to make you be responsible in lab, which is ridiculously terrible teaching, but seriously, you didn't do this with ether. It's not a strong enough mutagen, and you certainly wouldn't have seen all of those mutations arise from a few treatments. Mathematically impossible.
posted by amelioration at 3:03 PM on May 19, 2012 [6 favorites]

Thanks, amelioration.
posted by lilac girl at 4:14 PM on May 19, 2012

Shrimpsmalls - wow, the colleges I attended (for Genetics, no less!) don't even bother with actual fruit flies (for classroom learning - still use them for research, of course). We just used the virtual flylab!

ANYHOO. What is your fund situation? Carolina is my typical go-to for simple labs, especially ones I may not be THAT familiar with (to build my own), and they seem to have a lab kit for this:


no doubt they would have an instruction book detailing what you'd want to know, or you can call them.
posted by Lt. Bunny Wigglesworth at 5:59 PM on May 19, 2012

Erggg, I know html, I know html....

Drosophila Genetics Kit
posted by Lt. Bunny Wigglesworth at 6:00 PM on May 19, 2012

My son went to a science-based elementary school for advanced students and has taken science research classes continually since the 7th grade. His middle school created a science award especially to award it to him in 7th grade, and he won it again the following year. A guy from NASA came out and to give him another award that year and he's been placing in the regional science fair for years. Now finishing up his junior year in high school, he has just taken the AP biology test. He is planning to major in microbiology in college and has a special interest in epigenetics...the kid is into science in a BIG way, is what I am getting at here.

He just finished the drosophilia in his AP Biology class about 2 weeks ago and enjoyed it immensely, but said, and I quote, "That's WAY too advanced for junior high, gifted or not."

That said, I have the Super Duper Secret Science trick to doing this lab if you still decide to go ahead. Science Teachers, take note!


For each student, you just need 2 alka seltzer tablets dropped into a beaker filled with 300mg of water, and a tube from the seltzer mix to the fruit fly enclosure.

Knocks them out cold for about 20-30 minutes, so you can do what you need to do without worrying about the headache of introducing a classroom of precocious kids to ether, or traumatizing them withhosts of dead flies.

Your drosophilia can be stored, unconscious, on ice, for a surprising amount of time without doing them any damage, too. They might look dead, but they are actually fine.
posted by misha at 6:53 PM on May 19, 2012

"That's WAY too advanced for junior high, gifted or not."

I do have to agree with this, especially in such a short time frame. I don't even trust my college students with fruit flies, to be honest.

Are you married to the Drosophila idea? You could try "Fast Plants" - the entire lifecycle (flower to flower) takes about forty days, but there are genetic traits besides flowers that you can examine (stem color, bristles, etc.).

To speed things up you could also buy a set yourself and pre-fertilize them - cross some green stem to purple stems a week before the session, then have your students cross green stem to purple stem on the first day, and then the second or third day switch them out with the ones you've already fertilized. The students can then plant those and in a few days they should get shoots showing stem color. If you meet every day it will also give them something to do - they can monitor water levels and things like that.

Sorry for the unsolicited advice to change your lesson plan, but most non-microbial genetics will be pretty tricky to do in just two weeks because of generation times. It might be cool for YOU to do a demo fly lab (again, start the crosses ahead of time) and have the students sift through the results, but I would be very wary of letting the students work with the flies themselves, with only two weeks total.
posted by Lt. Bunny Wigglesworth at 8:36 PM on May 19, 2012

We worked with them in college and I seem to remember some stages where we had to visit the lab and work with the flies every 12 hours. Don't know if your activity would require this but might be problematic if it did. I also agree with those above that it is pretty advanced for your age group.
posted by leetheflea at 7:19 AM on May 20, 2012

I have run this lab a few dozen times with college students, and I agree completely with amelioration (above).

Sexing the flies is very, very difficult for beginners, and some students struggle mightily with this. I don't think gifted elementary school children will be able to do this with any degree of accuracy.

Worse, if they're not accurate about it, you've just wasted weeks and dozens of lives for nothing.

I think the idea of making this a demo is brilliant, and there are lots and lots of ways to make the demo exciting for the students. If you can get a scope camera set up to display what you're seeing in a microscope, students can watch as you sex and sort flies. They can tally phenotypes as well.
posted by yellowcandy at 9:08 AM on May 20, 2012

Response by poster: Thank you! I know that a previous instructor of this course did do a modified version of the lab with the same age group. I am trying to get in touch with him/her re the logistics. I like the idea of either doing it as a demo or just as a virtual lab. I just really want at least one proper, hands-on lab for this group, and this one kept coming up as the gold standard for the topic. I'm also going to look into the fast plants idea. Thanks again for all of your insights.
posted by shrimpsmalls at 7:11 PM on May 20, 2012

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