20.109(S18) Class blog

Your first meeting with the Comms Lab can be a bit confusing. You know you need help with your 20.109 homework, but you don’t know what they’ll be able to help you with.  Before you even schedule the meeting, it helps to find out a bit more about the available fellows. In my case, I found a BE fellow who was a TA for 20.109 in the past. This meant I didn’t have to explain as much about the assignment (it was a Methods section), and that she had a rough sense of the requirements/expectations of the assignment. At the end of the meeting we also had some time left over, so it was easy for me to bring up other assignments that were due soon, and for her to critique what I had so far. The second tip is to make sure to give your Fellow an overview of the assignment. Sometimes they’ve taken or TA’d 20.109, but other times they may not have much experience with the class. It helps to send them a link to the assignment’s rubric or requirements when you set up the meeting through ...

One of the things I’ve always found striking about biology is the juxtaposition between the clean concepts that we learn in lectures and the microscopic messiness of the physical reality.  The gap between theory and application is large because the multitude of nitpicky details are lost in a high-level explanation. Furthermore, the key concept of the procedure is often not actually visible when performing it. In affinity chromatography it’s easy to miss the actual step where FKBP12 binds to the His-tag, because the whole procedure is just combining different clear liquids with each other and centrifuging them for slightly varying amounts of time.  A really visceral understanding of this gap is one of the most valuable things that I have gotten out of 20.109, especially since a lot of 7.05’s material lined up really well with the theory behind our Mod 1 experiments. Some salient features of the day-to-day in the wetlab: Working with countless little tubes of clear liqu...

“Aaaaaah…..” “Oh, no!” (returning off the aspirator) “I’m sorry.” “What do we do?” (squeezing the aspirator tube) “Can we break the vacuum?” “Let’s pull together.” (pulling on the aspirator tube in two opposite directions unsuccessfully…) On the third day of Mod 1, my partner and I aspirated our +IPTG induced pellet. I was so convinced that we should aspirate the left over supernatant with an aspirator because it worked well for the –IPTG control pellet. Why did an n=1 experiment convince me that aspirating would be safe?  Consider a hypothetical situation where before any experimentation, I think there’s a 1/2 probability that the aspirator cannot aspirate a pellet, and 1/2 probability that aspirator can aspirate a pellet and does it half of the time. One successful aspiration should only increase the probability that the aspirator cannot aspirate a pellet to P conditional = 0.5/(0.5+0.25) = 2/3. So a successful aspiration should increase my confidence in aspira...