 This far in the class we've mostly focused on structure, but today we're gonna focus on sequence instead That might seem like taking a step back, but it's not really whereas structure is founded in the laws of physics and understanding Interactions today. We're rather gonna focus on the information and in particular the keyword evolution It's gonna turn out by the end of the class So that these are intimately related and I think it will benefit you to be able to look at this literally from both sides We are Gonna start with our classical old different ways of looking as it's sequence of primary sequence secondary structure tertiary and quaternary and primarily at the primary one as You hopefully know by now a Specific primary sequence will always lead to a particular structure of protein Why well that goes down to the central dogma of molecular biology, right? Sequence leads to structure leads to function. So if we have a particular protein Minor differences in sequence here due to the mutation that's gonna influence the overall structure And when we influence the overall structure, I'm gonna change say the ligand binding site And when I change the ligand binding site, that's gonna lead to a change in function possibly And if I get a change in function, that's then I'm gonna have this feedback loop Because if a particular function makes me more likely to survive I'm gonna have more offspring and that means that this variation will be more common at least after a few billion years This is also the key why we can look at things either from a physics point of view or an information point of view If we did not have this feedback loop There would no be no way of physics to feedback into the sequence in our genes, right? But because of the feedback after again was where's natural selection has done its work The information we have present in the primary sequence also includes Encodes depends on whatever you want to call it all the physical interaction And that means that I can look at this either in terms of patterns in the sequence or Exactly how those two atoms interact and that's gonna prove very valuable later today