Mendelian Genetics with Fastplants, Corn on the Cob, and Sickle Cell Anemia

We've been increasing our repertoire of labs that students can do as we're talking about Mendelian and non-Mendelian genetics.

One of the labs that we've done for two years now is with Fastplants. This is another lab I use from Lee Ferguson and is on her website here under the Mendelian genetics link. Since I have small classes, I only buy one set of F2 seeds and all of the lab groups germinate the same type of seeds. Then we pool all of our data to analyze it. Last year, we used the F2 crosses of purple vs. green stems, and green vs. yellow leaves. We had a terrible time distinguishing the color of leaves since purple stems make the yellow leaves look greener, and green stems make the green leaves look lighter. Although we had great germination rates, our ratios were not even close to the expected. In our class discussion of our results, we decided it was due to the difficulty in distinguishing leaf color.

This year, I decided to go with green vs. purple stem and dwarf vs. normal height. My students were pretty excited about how well the seeds germinated and how as they sorted them by phenotype how close the numbers were to the expected values. They were pretty stoked about how small their chi-squared value was for our class data. I love it when they get excited about this kind of stuff! I think part of it is that they often complete labs with fairly high percent errors, and it's actually satisfying for results to go so well. They all agreed that this was a great variety of seeds to analyze. I'll be ordering this variety again next year.

Another lab that allows us to look at the ratio of phenotypes in a dihybrid cross involves looking at ears of corn. I went to an APSI this summer and one of the labs that I won was a class set of ears of corn from a dihybrid cross involving yellow vs. purple and smooth vs. wrinkled.

The lab we use to analyze the ears is from Biologycorner.com and you can find it here.

Another activity that I've added to our genetics unit is from HHMI Biointeractive. We do the activity titled Mendelian Genetics, Probability, Pedigree, and Chi-Square Statistics and the teacher and student materials can be found here. We watch the short film first, that is also found on that page, and move onto the questions. I like the introduction to sickle cell anemia since we'll revisit it when we get to the natural selection unit. 

Jelly Bean Heredity

Last year when I was looking for a lab activity to help my students understand the basics of Mendelian Genetics I came across the hands-on activity, Heredity Mix and Match on teachengineering.org.

In my Advanced Life Science class last week we made jelly bean babies. In this lab investigation we're working on distinguishing genotypes from phenotypes and how they are interconnected. We also had discussions about being homozygous and heterozygous for a trait, and even squeezed in a few Punnet squares with a review of dominant and recessive genes. All the students enjoy naming their newly created baby and parents-even the ones I would have never guess would get into it.

I reformatted the Heredity Mix and Match from teachengineering.org into a Google Doc with a just a few minor changes.

Book-ending Christmas break with Lorenzo's Oil

Keeping students engaged on the last day before Christmas break can be a challenge, but I don't believe in wasting time.  We just finished our unit on Mendelian Genetics, and watching Lorenzo's Oil is a great complement to what we've done in AP Biology so far.  Last year I found a study unit on the movie here. We started with the activity demonstrating what happens to nerve signals as they become demyelinated. Students start with a "brain bucket full of signals (ping pong balls) and must pass them from one student to the next until it reaches the "body" bucket. We count how many signals (ping pong balls) make it into the body bucket in 10 seconds and then start again. But the second time
we do it, two students have to sit out and the remaining students may not move any closer to each other. We repeat one more time with two more students sitting out, to get a feel for how signal transmissions changes as more of the myelin is lost from nerve cells.

Then we get out the snacks and start watching the movie.  There are questions provided in the study unit to help them keep focused and delve deeper into the science of the movie.

When we get back from break we do the competitive inhibition activity with paper clips and finish the movie.  In the competitive inhibition activity we look at how providing more unsaturated fatty acids "competes" with the saturated fatty acids to hinder the production of very long chain saturated fatty acids (VLCSFA).

As we finish the movie, it leads naturally into a discussion of medical ethics, and is a great segue into our molecular genetics unit.