This is always one of the favorite topics of the semester – Mendelian genetics, and inheritance. We cover a bunch of really interesting stuff, including questions like:
- “Can two brown-haired people have a blond baby?”
- “Why do I have green eyes and my sister has blue eyes?”
- “Do twins have the exact same DNA?”
- “What are the genes that determine how you look?”
- “Can you choose which traits your child will have?”
We also talk about pedigree analysis, and inherited diseases, and Punnett squares (okay, they don’t usually love Punnett squares haha). But still, loads of cool stuff! My lectures on the topic are pretty well set, but I needed to figure out some lab activities. The one activity I use with my lecture-only course is designed as a homework activity, but it was pretty simple to restructure it into a rotation lab. I also found a few additional things for them to do, and explore the subject of inheritance.
Right from the start, they figure out that this isn’t going to be just any old inheritance lecture. When explaining Mendel’s breeding experiments, I make a very minor adjustment . . . instead of all those pea plants, we pretend that he was breeding dragons. Mostly because I like dragons a lot, but it also ties in with the hands-on activity I had them do later in the day. 😀
We didn’t jump right into dragons with our lab activities, though . . . we started out breeding dogs, instead. I found this really cool online activity at PBS Kids, and created a worksheet to accompany it. We took a trip over to the library, so they could use school computers, and they all got busy trying to breed dogs with desired traits.
The rest of the day’s activities I sort of switched around on the fly, as I decided I didn’t really like my original plan. So, I’ll describe what we actually did, and I’m not going to post all of the worksheets, as I ended up doing activities in a different order.
Before lunch, we did an activity on inheritance of human traits, where they assessed their own phenotype for several different classic “monogenic” traits. (In reality, many of these are probably determined by multiple genes, but I think the activity still has value).
In addition to the ones listed above, I had a station for phenylthiocarbamide (PTC). I provided strips of paper soaked in PTC, and by touching it to their tongues, students were able to discover whether or not they have the gene that allows them to taste the compound. (Of course, the ones who could taste instantly regretted it – apparently it taste AWFUL. I wouldn’t know – I don’t have the tasting gene). Interestingly enough, I had two students who appear to be heterozygotes – they could taste the PTC, but only mildly.
I asked them to add their results to a chart that tracked the entire class, so we could play around with percentages. Of course, we’re not able to make any strong statements about our results, as a sample size of 11 is pretty small.
We did have one super interesting result though – two of the students in class shared the same phenotype for EVERY SINGLE ONE of the traits. The probability of that is less than 1% (roughly 0.78%). My hypothesis? They were unknowingly separated at birth. 😉
After lunch, we go to the really fun stuff . . . the DRAGON GENETICS ROTATION LAB! As I mentioned, I usually assign this activity as a homework assignment, but it transitioned perfectly into a rotation lab. At the earlier stations, students practiced things like Punnett Squares, and interpreting pedigree charts. Then, they were able to breed a baby dragon of their own. They’re given information for how several characters are inherited, and they flip a coin to determine which allele the baby inherited from mom, and another coin flip to determine the allele from dad.
Of course, there’s not really much point in determining the baby’s alleles if we never get to SEE the baby, so the final step is to create a phenotypically-accurate dragon. Usually, when doing this for homework, students visit one of the Doll Divine sites, and make a dragon there. In class, though, I turned it into an arts and crafts project. I gave everyone a template with a generic dragon, and all the possible traits, and a huge box of colored pencils, some scissors, and glue sticks . . . and let them go to town.
The verdict? Coloring is fun. 😀
After finishing up with the activity, we still had about an hour left of class time, so I started my Darwin lecture. It’s one of my best lectures, and usually keeps a class’s attention pretty easily . . . but about 20 minutes in, I saw that I was losing them. They were getting sleepy-eyed, and slumping to the side . . . so I found a good breaking off point, and decided to pick it back up in the morning. I suppose that breeding dragons is hard work. 😉