Here’s the next step in our genetics lab experiment, crossing brown-eyed and scarlet-eyed flies.
What will the hybrid F1s look like?
Pharyngula
Evolution, development, and random biological ejaculations from a godless liberal
Here’s the next step in our genetics lab experiment, crossing brown-eyed and scarlet-eyed flies.
What will the hybrid F1s look like?
I’ve been teaching non-stop all day, and boy are my brains tired. I end this exhausting day by dumping today’s genetics lecture on the world.
I should probably go to bed soon.
I keep telling my students about what I call Fly Time — the idea that these genetic experiments we’re doing require that we carry out the steps on the fly’s schedule, which may sometimes be inconvenient for the human experimenter. We’ll be flexible, but the work does require doing things outside the formally scheduled class time. That’s about to bite me in the butt.
We had this minor fire yesterday that canceled labs for the day. But we’re on Fly Time! They don’t care about our lab schedule! I’ve got a big plan that requires starting on time, and if we don’t begin the experiment this week it won’t culminate before spring break. I can’t compel students to stay and do lab work over their break, so if it runs over…I’m the guy who has to do all the final fly counts in the experiment. The students need to start the cross this week!
To accommodate our students’ busy schedules, I get to spend today in the fly lab helping a string of students coming in on Student Time to learn fly husbandry. All day long. Parked in a lab as students dribble in. Except for the time I get to spend lecturing them in class. And then I come home and put the recording of the lecture together and upload it. I also have to assemble a new problem set and post it on Canvas. Maybe if there’s a gap in the stream of students I can do that during the day?
Ha ha. The flexibility I’m trying to build into the course is coming out of my hide. There better not be any more fires this semester.
I said I was going to optimize my classroom management for flexibility, but this is ridiculous. I’m supposed to be teaching a lab right now, but the science building caught fire.
It was more of a tiny smolder, but we did get a lot of smoke in the building. I heard that plumbers were soldering some pipes in the ceiling, and something caught fire, and now the fire department kicked everyone out of the building and are trying to make sure there is nothing else burning in that space before they let us back in. “A few more hours,” the fire person said. So I had to cancel lab.
Now the next few days are wrecked for me, because I’m trying to accommodate a lot of busy students and persuade them to come in at some other time so we can get this cross started. I’m going to have to provide supervised lab access all day tomorrow and Thursday.
I swear, this job is trying to break me, but honestly, I’m already broken.
I can see my future now, for at least the next four months. I have committed myself to record all of my lectures so the students have asynchronous access to the course content to maximize flexibility in case pandemic catastrophe strikes, so what I’ve got to do is:
There are always glitches. Last week, the audio recording of the lecture was unlistenable, so I had to re-record the whole thing. That was better (but far from perfect) today. Today, though, the in-class technology threw up a whole bunch of problems — nothing worked until I called in IT to fix it, so I lost over 10 minutes to annoying problems. I intensely dislike the way the university has configured the AV in our classrooms.
So anyway, here’s today’s lecture. It’s about chromosomes.
Hooray for me! I got step #4 of my to-do list, and also step #3.
Tomorrow I’ll go back and get #2 (“Record a video summary of the fly culturing procedure”) done, and also #6 (“edit the fly culture video”), and then on to chromosomes, mitosis, and meiosis. I’m trying hard to build up slowly with a solid foundation before we get to the hard stuff.
All the final exams have been turned in, so now it’s time to sit my butt down and read them all. I’ve got two classes with about 25 students each, so here’s what I am to complete this weekend. These were all due on Friday, yesterday.
Comprehensive Final Exam for Fundamentals of Genetics, Evolution, and Development. This is the monster, 7 pages of questions in different formats that cover the topics in the title of the course and also a bit of the history and philosophy of science. FunGenEvoDevo is a first year overview course that doesn’t dig too deeply, but prepares them with the general background (there is also another intro course, Evolution of Biodiversity, that hits them with evolution again and also basics of ecology and systematics). I started on this one yesterday, and am a bit more than halfway through; I plan to finish it by this afternoon.
Lab Final for Cell Biology. Another longish exam, this one emphasizes basic quantitative skills they should have learned in the lab. So lots of questions about unit conversions, calculating concentrations, interpreting data, etc. For instance, they get some measurements of reaction rates, and they then have to calculate enzymatic Km and Vmax. There are a lot of parts to this one, too, but most of the answers are short, specific, and numeric, which are relatively easy to grade.
Required Final Essay for Cell Biology. Oh boy, this will be challenging. I gave them a paper to read (“How energy flow shapes cell evolution” by Nick Lane) and asked them to summarize it and relate it all to the content of the course. On this one, I demand high writing standards and coherence in addressing the subject, so we’ll see how that goes.
Optional Final Exam for Cell Biology. Another big ol’ comprehensive exam, but this one is optional for the students: whatever score they get on the final will replace their lowest midterm score. Everyone has a bad day, so this is their opportunity to vindicate themselves. It’s a long exam, but grading it might not be too bad — only about a third of the class has opted to do it.
So that’s my weekend! This is all I’m doing for a few days. I hope to get it all done by Sunday evening and get all those grades submitted to the registrar early.
Then on Monday I have one more class to grade, Biological Communications II, in which students spend the semester writing a 10+ page review paper under my tutelage, so I already have a good idea of what they’ve done — I just have to go over what is supposed to be the final polished draft of the paper. And then I’m ALL DONE!
I guess I better buckle down and get to work now.
10:45 Saturday: FunGenEvoDevo done! Grades submitted! Students mostly did OK, but a few of them may have learned that skipping an exam or two is a good way to fail a course.
3:45 Saturday: Lab final done! Starting on the required final essay.
1pm Sunday: Required lab final done! Now to polish off the optional final.
Good for me! I got all of the finals for all of my classes composed and sent off to the students (they’re all take-home exams). Now I’m all done with this semester except…all three of them are due on the same day, Thursday, which is just by chance the officially scheduled day for all of my class finals. Friday and this weekend are not going to be happy times for yours truly.
Until then, though, I’m kind of at loose ends. Four whole days with no class obligations hanging over my head, which feels very strange, and like there’s something wrong here. So I started getting ready for my spring genetics course, ordering flies, organizing my calendar, thinking about rewriting a bunch of my lectures, etc., etc., etc.
And just generally feeling like I’m heading into a savage storm a few days from now…
Yes! Almost done! I get to dismiss the class, and then move on to … composing the final exam, and then grading the exams next week. And then getting ready for Genetics in the spring.
I won’t be saying goodbye to the students, though. They’re mostly 2nd year students, and this is a small university, so we’ll all be seeing each other again (cue groans from the class who are struggling with the material right now.)
Yesterday, I gave my first year students a teeny-tiny quiz over the current unit in basic genetics. No biggie, I’d been hearing some troubling concerns from the class tutor that some of the students were struggling, so this was more of an assessment of how well they were grasping the simplest concepts in Mendelian genetics. Here, I’ll even let you see the entirety of the quiz: 5 questions, 2 points each.
You have a true-breeding diploid organism with the phenotype AB, and a second true-breeding organism with the phenotype ab. A is dominant to a, and B is dominant to b.
- What are the genotypes of these two creatures?
- You cross these two and obtain a clutch of F1s. What are their genotypes and phenotypes?
- You cross two of the F1s with each other. Predict what the phenotypes and their proportions in the next generation should be, assuming that Mendel’s laws apply.
- You cross one of the F1s with another organism that has the phenotype ab. Predict what the phenotypes and their proportions in the next generation should be, assuming that Mendel’s laws apply.
- You actually do the experiment in #4, you get the following results:
AB: 35%
Ab: 15%
aB: 15%
ab: 35%
Interpret this distribution.
See? If you were a student who’d just suffered through 3 weeks of an introduction to genetics, you’d probably have absolutely no problem with this. If you’ve been teaching genetics for a few decades, you could answer this quiz in seconds, in your sleep, while standing on your head. I think that might be part of the problem, because this is stuff I can totally take for granted.
I gave the students 20 minutes. Most of them used the entirety of that time. I scored the quiz that afternoon, and was aghast: mean score was 2.7/10, high score was 8. Yikes. How…? Where have I gone wrong? These are smart, hard-working students, and they missed everything. Then I saw the problem. The quizzes were covered with…
PUNNETT SQUARES. Jesus. They tried to solve every problem with a 4×4 Punnett square, which is insane. Punnett squares are a tool for graphically illustrating the outcome of a cross. They are not tools for calculating the results. They are a terrible, slow, clumsy tool for doing that. The textbook is full of ’em, I think because they’re easy to draw and give the illusion of a comprehensive answer. I’d shown a few in class, because I had to explain what the textbook was showing them, but I always told them that Punnett squares were terrible and useless, but this is what they knew, probably from high school, and then reinforced by the text, and then I made the mistake of trying to explain what the book figures were showing, and they came away with the impression that this is what geneticists do. It is not. Mendelian genetics are dead simple. You can just treat each locus independently (and they’re trivial, you can memorize all the possible results if you can hold 3 frequencies in your head), solve for A, solve for B, multiply to get the answer for A & B.
Christ, they’re trying to mechanically brute-force a solution with 4×4 Punnett squares, and it’s a disaster.
I can’t blame the students, though, it’s all on me. I remember being their age and taking Dr Sandler’s genetics course at the UW, and struggling for the first few weeks, until suddenly the light bulb flicked on in my head and I saw how easy Mendel was, and then when he started layering on the advanced stuff, like segregation distorters and epistatic interactions (seriously, try solving those kinds of problems with a Punnett square — you might be able to assemble some kind of nightmarish diagram, but it’s not efficient. You can’t even do linkage with a Punnett square.), it was all just an easy arithmetic modifier added on to the basic concept. But then, Sandler was a brilliant teacher, I’ve got some catching up to do.
So how to deal with this problem…next week, I’m going to rewind and go back to the basics, review these elementary problems without Punnett squares anywhere in sight, and actively tell the students that Reginald C. Punnett was of the devil, put on this Earth to confound generations of genetics students. Then, over Christmas break, I’m going to back over my stored presentations and notes and edit out every mention of the P word. Maybe I should print one out so I can put it on the floor the first day of class and piss all over it — nah, some administrator would probably complain.
Then, you out there — yeah, YOU, high school teachers and textbook publishers — stop poisoning students minds with these abominations. I’ve never liked them, but I keep using them because they are traditional, and because the books and students come with them preloaded. Just stop it. They’re pedagogically bad. I’ve got to explicitly unteach them now.
This is a tragic setback, because what my plan for the course was saying is that I start next week on the developmental biology unit, my favorite stuff, and now it’s getting bounced back two weeks, and is going to get slammed up against the end of the term. I’m going to blame Punnett.
