 Hi, you guys. So we started out this session talking about energy. And hopefully at the end of what you've done so far, you have a good sense of how complex and critical cellular processes dealing with energy really are. We're about to dive into a topic that is equally complex and equally critical. So we're going to look at DNA, which is the molecule found in the nucleus of your cell. And it's responsible for, it carries all the information that makes you who you are. We're going to look, we're going to spend three lectures talking about DNA. In the beginning, we're going to look a little bit at the history. We're going to look at what it's made out of. We're going to look at how DNA makes a copy of itself. If you think about it, every single time one of your cells replicates or divides, and this is a process we're actually going to look at in the next chunk of topics, but every single time a cell divides, when you grow or replace old worn out cells, you're going to have to make a copy of your entire genome. Every single part of your DNA, you need to make a copy for the new cell. And that really important process is what we're going to talk about today. So I think it's nice to have some historical perspective when it comes to DNA. Hopefully, when you think about the molecule, you already are like, oh yeah, DNA. It's that double helix thing. It's really pretty and it is really important. Carries all the information in it that makes you who you are. But it wasn't that long ago that people, scientists really weren't sure if they weren't sure if it was DNA or if it was protein that carried the hereditary information. They did know that it was carried in the chromosomes. However, when we start looking at what chromosomes are made out of, chromosomes actually have proteins in them. So it makes sense that a chromosome, you know, the chromosome itself, we still would have confusion. It might be the protein in the chromosome that is responsible for hereditary information. It also was known that proteins, that there were some heritable conditions, diseases, that involved a malfunctioning protein or enzyme. And that made people think, oh, you know, proteins are the molecule responsible for heredity. Well, we're going to explore DNA and realize that they're actually really closely linked. But DNA is the molecule that contains the hereditary information. Once the research was done that concluded this, and this was like, I don't know, in the early 1900s, that they basically, or in like 1940, they came up with, okay, pretty solid evidence that indicated, you know, DNA is probably the hereditary molecule. Then the interesting thing became, well, what is the structure of DNA? What is it actually, like how does it do this? How does it carry the hereditary information? And so that's what we're going to talk about first. How do they figure out the structure of DNA?