Summer SAVY, Session 1 Day 3, Molecular Genetics (5th-6th)
Today we were busy. We started with a four corners getting-to-know-you activity and a review of the previous days. Then we began our study of evolution with a discussion of Charles Darwin and his journey on the H.M.S. Beagle. One of their stops was the island of Mauritius, where Dodos were endemic. They learned that by the time Darwin was there in 1836, the Dodos were already extinct. Speaking of extinction, we were in the computer lab after ORA running simulations of natural selection with hypothetical critters and a changing environment. They ran the simulation several times and saw that they didn’t always get the same outcome. Sometimes there was a disease outbreak, a volcanic eruption, or a drastic change in the climate. We discussed how the outcome of evolution is impacted by relatively random events, including genetic mutations, sometimes leading to extinction. They will probably want to tell you about the “computer game”.
After the computer lab, we went out onto the Peabody Quad and thought about organisms and adaptations. Students were tasked with identifying an adaptation in an organism. They were challenged by this at first, but I think I was able to convince them that adaptations are everywhere. Here is a wood-rotting fungus that one student found and a nice dormant lichen specimen. We talked about adaptations and what it means for a trait to be adaptive.
Encourage your molecular geneticist to consider the environment and how natural selection has shaped our world, and how we have shaped the world via artificial selection. What adaptive traits do your pets have? What traits are maladaptive? If they were going to create a breed of dog, what traits would they want in that breed?
After lunch, we studied the structure of DNA and some of the people involved with figuring this out, including Watson & Crick, Rosalind Franklin, Maurice Wilkins, and Erwin Chargaff. Students then built a model using Twizzlers, mini-marshmallows, and toothpicks. Their model may or may not have made it home intact. Students also learned about the base-pairing rules and the idea of the nucleotide or DNA sequence. At that point, we looked at a karyotype, a picture of the arranged pairs of chromosomes, and they gained an appreciation for the amount of DNA that we have in each cell and that nucleic acids are large molecules.
We finished the day with a preview of tomorrow morning’s activity, which is gel electrophoresis. I showed them the apparatus (MiniOne) and stressed the importance of being careful with the equipment and paying attention to detail. I have not done electrophoresis with students this young, but I think they can handle it. We’ll be testing real DNA samples for the presence or absence of the sickle cell mutation. Is the person free of the mutated gene; are they heterozygous; do they have sickle cell disease? This is a nice lead-in to their project on a genetic disease/condition, which they will begin working on tomorrow.
