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Day 8: Females > Males

I may have infused some sociological norms into today’s activity. Do boys really prefer blue? Or is it a social construct? Hmmm…

What does this have to do with day 8 of our fly genetics project? Well today students had the menial task of transferring their flies (and they will do it again Thursday before Finals are over) from their original culture tubes to new ones with fresh yeast and less dead flies (I equated it to a human living in a clear trash can with half-eaten food and dead things, after that they felt like it was necessary). Some students had only one fly left. Luckily, in all but one of them that fly was female. Why is that ok? Well it’s probably pregnant and will lay eggs. As far as we know, the males won’t lay eggs, so today females were better than males.

Students knocked flies down to the bottom of the original tube (by tapping the butt on the table) and then removing the cotton and turning the new one upside-down and placing it over the opening of the old one. Like so:

photo
Old on bottom, new on top

Then of course, the Drosophila move upwards (gravitaxis anyone!?) towards the new vial. Then we turned the new one over and capped both with cotton. It then got a new label with the same genetic cross tag, student names, class period, and the NEW date.

However, we kept both vials as it’s possible our viable flies already laid eggs in the old culture tube and we don’t want to dispose of them. So now students get to take care of two tubes and by Thursday they will take the day 8 tube (today’s) and transfer it to a new tube. Then all the flies will take a 2 week hiatus and by the time we come back in January we will “hopefully” have a whole new business of flies. See you next year!

Day Five: Punnett Squares FTW/L?

Alright, long weekend involving buying a car (bye money) left me a bit overwhelmed. But let’s update from last Friday.

First, students were asked at the beginning of the hour to (1) label posterior, anterior, lateral, dorsal, ventral on a fly diagram and (2) the stages of the Drosophila life cycle along with time at each stage. For the most part they nailed it. A couple more days and it will be ingrained.

We then went to the dissecting scopes to check out day 5 of development and we certainly heard the most excitement of students so far. Their (relatively) tiny larva had grown to twice their size and now under 30x magnification they appeared to be monsters. (Which provided some entertainment when unsuspecting students peered first at them under 30x unknowingly). What did students see? Here’s a great student video:

http://www.youtube.com/watch?v=_8-JxerP1rw&feature=youtu.be

What structures could students see? Trachea (lines running down the larva), mouthparts/head skeleton (dark spot-anterior), and spiracles (orangish spots-posterior).

30x magnification

After that, we asked students to remind us what traits they saw universally in these flies that looked abnormal from what you typically expect to see in fruit flies. The two mutations that at least a couple observant students caught was the orange eyes and curly wings. We then explained that these mutations were caused by the same gene, cyoYFP (cy = curly; o = orange; YFP = yellow fluorescent protein [not explained today what that was for]) Then we explained that this gene was on the 2nd (of 4) chromosome on the fruit fly. Furthermore, we asked how many chromosomes each fly has in each set (A: 2, like humans). So then we told them that the 2nd homolog of the 2nd chromosome (make sense?) was a balancer chromosome and that this chromosome contained the cyoYFP gene. Basically, this balancer chromosomes (AP Bio had to explaing TO US what these were through the magic of research [and Google]) does three unique things: 1) It prevents crossing over and therefore genetic variation, 2) It allows us to track the mutation through many generations, and 3) It only creates heterozygotes.

We also mentioned that the whole point of this research project was to characterize the function of the Tep3 protein and the gene for it was on the non-balancer homolog of the 2nd chromosome. So that led students to the question, “What would we only see heterozygotes?” What happens we we get Tep3/Tep3 or cyoYFP/cyoYFP individuals? To channel someone near and dear to all of us, “Sounds like an experiment.”*

This is when we had a boy and a girl (volunteered or otherwise) come up to the board to represent the mother and father fly. The father had the genotype Tep3/cyoYFP and the mother also had the genotype Tep3/cyoYFP. So what genotype combinations would we expect to see in the offspring? We asked the freshman students how many chromosomes get passed on from each parent. Predictably they answered 1 (or half). So they wrote the genes they could pass. Either Tep3 from the 1st homolog, or cyoYFP from the other. Then we asked, “What combination of offspring could we get?” The students wrote those on the board (pic below).

Mendelian Genetics in 2 seconds

Oh yeah, did I mention Punnett Squares? Some (clever?) students realized this combinations could have found out using Punnett Squares. Some of course when seeing this made them, but others were confused by using gene names and not big-A and little-a. But those same students who were confused by the gene name abbreviation were able to generate the combinations without using Punnett Squares. So we were still left at the crossroads of a timeless debate: To Punnett or not to Punnett? (COMMENTS SECTION!!)

But after this we asked students how we would in real life set up these combinations. They determined we probably needed male and female flies in the same vicinity. I asked if a large jar would do. They said that that would not provide good data *tear drop* so we should make multiple iterations. We gave them each a vial and they were charged with the task of finding 6 females and 5 males to put in the vial.** After that they labeled their vials with the cross (Tep3/cyoYFP x Tep3/cyoYFP), their name (w/ partner), and hour.

AP had the added excitement of creating the control setup, because we still had to determine if cyoYFP was a dominant or recessive allele. They accomplished this by using a Gal4 gene.

Monday we will be transferring flies to new vials, same for Thursday (post-final fun) and then their little ones will incubate for the remainder of winter break when they’ll see the product of their crosses when they return.

*Yes, I really did say that to them. It felt odd, but cool.

**Now, unfortunately, no student (AP or freshman) picked up on the fact that these flies had been already cohabiting the same vials, therefore the females they chose most likely did not need a male, they were already pregnant. This exercise was to help them get used to crossing flies and predicting the outcomes, nevertheless I thought one student (and they still could) would catch this flaw.

Day 2: Where are my larva?

Today our larva hatched from their eggshell and began crawling around.

Students were first asked to recall and attempt to diagram the anatomical positions (anterior, posterior, dorsal, ventral, lateral) on pictures of 3 different stages of development (embryo, larva, adult) as well as identify which stage was which picture.

We then showed students a video from DNATube that showed the development of the embryo to the first instar over the last 24 hours. Basically, we wanted students to understand that something was happening between yesterday and today and it has a really good time-lapse of segmentation, folding, and migrating of cells in it as well.

Students then found their apple juice agar plates from yesterday and looked to see what had happened over night. To their surprise, “nothing had happened” because their eggshells, including dorsal appendages, were still present. This was an unexpected moment on my part, but they thought their flies had died. It finally took a student or two shouting, “I found some moving!” and with some prompting they described they were by the yeast paste, not their eggshells (which most had forgotten were shells and not part of the epithelium that grew with the fly. After that hurdle, most students began making great observations, observing feeding, movement, social behavior between multiple larva.

Once students had observed and documented the change in their larva, we then moved to adults so students would be familiar with them since they will have adults next week when they set up their crosses for over winter break. First, we reviewed what male and female fruit flies looked like (Freshman had been assigned to watch this video last night; AP was given the task of figuring out by using observations and the internet which sex was which) and then they were given the task of sorting through about 15 flies we had put to sleep with FlyNap in petri dishes into male and female groups. If you need a refresher, here’s a photo (this was also a good example of why we discouraged students from using size as a determining factor for sex):

photo 2
These flies signed their photo release.

Some students even got to witness the miracle of life (can you figure out the sex now?):

photo 3
It’s so beautiful.

After separating male from female it was about time to go so with our last couple minutes we asked students to share their observations about what was SIMILAR between all of their fruit flies and to my astonishment about every class had the two picked out very quickly. That would be the orange eyes and curly wings, which are mutant phenotypes (wildtype being red eyes and straight wings). We left the freshman with that and told them we would discuss further their genetics on Friday while AP students were given the task of beginning to research Balancer Chromosomes, with the tip that this was essential to understanding these mutations, since they had a little more time left.

Tomorrow and Thursday are off days, we’ll be back researchin’ on Friday!

NGSS lawsuit

I appeared on the radio show, Voices of Reason, on KKFI, 90.1 FM, on Dec. 1, to discuss the lawsuit attempting to prevent the implementation of NGSS. In a twist of history, I find myself defending the actions of the state board on evolution instead of protesting. Nevertheless, we can’t allow ourselves to fall asleep on this matter. Only the first 39 minutes of the attached show deal with this issue.

Day 1: Fly Genetics

In an effort to channel Brad earlier this fall, I will (hopefully) be blogging about an ongoing interdisciplinary project a researcher and I are currently working on. The blog posts are hosted also on my blog and therefore may contain odd wording or obvious/redundant information, but partly this is for my memory as well as an audience possibly unfamiliar with genetics. All photos are mine or credited to their owner and any information published is with the permission of my researcher as well as we hope to publish our approach as a way to illustrate collaboration between secondary and post-secondary institutions. Enjoy:

Today marks the beginning of what I think it going to be a really cool project for my students. Through a connection at at the University of Kansas I and a PhD candidate my students (both freshman and AP biology students) will be embarking on an 2-month interdisciplinary project.

Basically, students will be attempting to characterize a protein involved in epithelial cell stabilization (specifically a protein in the septate junction of Drosophila melanogaster).

Today was technically day 1 (the researcher came by last Monday and met the students and introduced their research focus and what they’ll be doing as an overview).

First, students tried to recall Drosophila epithelial cell structure and function, which surprisingly they all remembered, at least the essential components. They remembered how to draw the cells and that there were “walls” involved that separated the chemicals from the apical (outside) and basal (inside) regions. The names we can hammer in later, but that conceptual understanding was nice to see.

We then had students go to their dissecting scopes to observe their embryos for the first time. This was also just the second time students had used dissecting scopes this year so they were getting a lot of new experiences. Students were viewing multiple embryos on apple juice agar plates with yeast (for food).

apple juice plate w/ yeast paste on right, flies on left

apple juice plate w/ yeast paste on right, flies on left

Students were given the task of drawing what they saw (we did not tell them they were fly embryos, just to look and observe) using a petri dish outline in their composition notebooks for drawing their field of view. Of course, I showed students once again the awesomeness of their camera-phones which did it’s usual trick of instantly turning some students into microphotographers! Here is one of the better photos:

embryos day 1
30x magnification
Can you see their dorsal appendages?

So after students decided we had embryos, we showed them the rest of the fly life cycle (below) and asked, what do you expect to see tomorrow? They decided they would see larva and we asked what they expected to larva to do? Once they said moving some students shouted, “Some of mine are moving!” Then we had that student draw what they saw of the moving fly and it got most others excited for some movement tomorrow. What was fun (I thoughtwas when we asked students based on this molt hormone’s levels through the flies life, what stage of human life correlates with the giant spike in hormones for pupa? (A: PUBERTY! Gotta love that reaction from 14 years olds

Drosophila Life Cycle (w/ a molt hormone levels throughout)

Then the last thing we did was we had volunteers one by one draw components (example below) of the Drosophila anatomy, so that we could use a common terminology when communicating throughout the project. For the freshman it may have involved mimicing antlers to remember anterior and even one dedicated teacher lying on a table dorsal side up (image not found) so students could visualize how they were viewing their embryos from their dissecting scopes.

student fly anatomy drawing

So with that (rinse, repeat 5 times), day one was complete and day two is tomorrow! Stay tuned!