What a session!

Power was shy this morning, and our students also started slow, but hey, those nucleic acids give a lot to talk about and after a while, the class was full of scientific talk again. Ponch has gone over the molecular basis of DNA and has done a nice overview of the processes of replication, transcription and translation. Transcription and its nomenclature, the template and the coding strand, who invented those names! Actually, yes, there are many concepts, but if you think about it slowly, it all makes sense.

The “coding sequence” of the DNA is the one that contains THE CODE, e.g. the one that tells you how the protein is going to be. The difficulty comes when we are given the existing tools for copying DNA into mRNA (the messenger that is going to take the information to the ribosomes in the cytoplasm so they can make the protein). The RNA polymerase can only make a complementary strand to the chain of DNA that is copying, like a mirror image. Therefore, if we copy the “coding strand” we will loose the code; we would have to read through a mirror, like when we read Leonardo’s work, and ribosomes can’t do that. But nature found an amazing way to solve this, and Watson and Crick gave us the gift of revealing it: the DNA is a double helix of two complementary strands and opposite to every coding strand, we have a template strand which is called like that because when the polymerase uses this strand as template, the emerging RNA carries the CODE.

Now, if you thought the discussion was over when we got there, ha! You should have seen the conversation that took place afterwards, starting with what is a chromosome, following with those naughty genes, and comments on how all our cells, which carry the same information! are so different to each other. We finished with a few of those videos that are making biology easier everyday for those of us that are useless when it comes to imagine 3D structures. I think we got a pretty good understanding of the processes that allow for genetic information to be kept and used. We'll get tomorrow into how that use can be (it has to be!) regulated.

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