11/27/2023 0 Comments Building blocks of dna and rna![]() There’s a sugar, a five carbon sugar, which forms the core of the nucleotide and attached to this five carbon sugar at specific positions on the sugar relative to this oxygen, which is part of the sugar ring, is a phosphate group and an organic base. So the repeating unit in DNA is this structure here, a nucleotide, which has three different regions. Nucleic acids, of which DNA is an example, are polymers of nucleotides. Cross-linked is not the right word–that is chemically bonded with repeat units to make large molecules so that when you have a bunch of large molecules together they have certain physical properties like the solid property of the plastic that you’re sitting on. We’re familiar with polymers, plastics in our daily life the chairs that you’re sitting on are made of a kind of a plastic polymer that is basically an organic chemical that is cross-linked together. A polymer is just a large molecule that’s made up of repeated units. The molecules that really make up DNA are nucleotides and DNA is a polymer of nucleotides. You’re going to know more details about it, they’re not really colors, they’re chemicals, specific chemicals - but the pattern is the same. The things that you need to know are the things that are really listed on this slide. That’s what I want to do for the first few minutes of the lecture here is tell you a little bit about the details of the structure and how molecules fit into this image of DNA that’s already very familiar to you. This is a feature of DNA shown in this cartoon form, so if you can keep that sort of schematic in mind, it makes it a lot easier to understand the detailed structure. You don’t see a red and yellow, you don’t see green and blue. That there are two colors per strut, so what’s linking the two backbones together are two colored segments that come from the outside towards the middle, and that the colors occur only in certain combinations, red and green, yellow and blue, that’s all you see. One is that there’s four different colors and so you can see red, blue, yellow, green here - four different colors and that’s all there are, there aren’t more than four. There are several things that you’ll notice about the struts in this particular cartoon. ![]() On the inside are the rungs or the struts that hold the ladder together. The backbone’s on the outside of the molecule like the upright struts of a ladder on the outside of a ladder. One thing to notice is this part of the double helix that we’ll call the backbone. Those are two continuous strands that wind around each other to form the double helix. One is that there are two backbones right here in the light blue, so this would be the upright parts of the ladder that are twisted. It’s a twisted ladder and there’s a couple of things to notice about this familiar structure. I want to start by showing you this cartoon that you already know about with the structure of a double helix. It’s really remarkable how far–how fast we have come from just knowing the structure of this molecule to be able to manipulate it and study it in great detail. Building Blocks of DNA ĭNA is a double helix, you know this, the double helix was–the structure of DNA was discovered about the time that I was born and so it’s been known throughout your lifetime, you’ve always lived with it. Then on Thursday we’re going to start talking about how to manipulate DNA and get closer to using it in Biomedical Engineering. So my goal today is to talk about sort of the basics of the molecules, their chemistry, the function of DNA in cells, sort of basic - the basic side of that. We’ll talk about some chemistry today, what DNA molecules are like, why they have the behavior that they do, and you need to understand this in order to understand how you manipulate DNA. I think the book has a fairly good description of it so if you don’t pick up everything in the lecture, hopefully you’ve read that beforehand, and you can go back to it afterwards and read about things that didn’t make sense. I’m going to ask you to indulge me while I go back to the beginning and talk about some things that you know but I’m going to go through this pretty rapidly. In fact, even if you haven’t had a biology class it’s hard to be alive in 2008 and not know something about DNA it’s become such an important part of our lives. ![]() Some of this will be familiar to some of you who’ve have had biology in high school or other places, you know something about DNA. Professor Mark Saltzman: This week we’re going to talk about DNA technology and genetic engineering: this is Chapter 3 of the book. Frontiers of Biomedical Engineering BENG 100 - Lecture 3 - Genetic Engineering
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