Discovering the Structure of DNA

by Jason Amores Sumpter
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in this video, we're going to talk about some of the scientists that helped with discovering the structure of DNA. And so way back in the early 19 fifties, Ah, female scientist named Rosalind Franklin actually used a technique called X ray diffraction on DNA. And she used X ray diffraction on DNA to capture an incredibly important photo that is well known as photo 51. And so, if we take a look at our image down below, over here on the left hand side, you can see an image of the scientist Rosalind Franklin, And you can also see an image of Franklin's Photo 51 which again is showing an X ray diffraction pattern of DNA. And so what you'll notice is in this X ray diffraction pattern. These bands, uh, that create this kind of X like formation, and so through very, very complicated concepts and math. Uh, it turns out that this photo 51 here is actually evidence to show that DNA has a double helix structure. However, it wasn't until the 1953 that the scientists, James Watson and Francis Crick, actually were able to use Franklin's photo along with other information that they knew toe help them describe the structure of DNA. And so they described DNA as a double helix structure with two anti parallel strands of nucleotides. And so, of course, this is information that we had already covered in some of our previous lesson videos when we first introduced DNA. And so, if you don't remember three information from those older videos on DNA, be sure to go back and check out those older videos on DNA. Now Watson and Crick had also come up with how these base pairing rules apply. And so it's known as Watson and Crick base pairing. And so Watson and Crick, basic comparing, basically describes how the nucleotides on opposite strands of DNA will actually pair with each other via hydrogen bonds, where all of the ad innings, or ACE, would base. Pair with all of the thigh means or tease on opposite strains and all of the side of scenes would base pair and hydrogen bond with all of the guanine means on opposite strands. Sow seeds, base pair with GS. And so this is gonna be really important information for you guys to be able to keep in mind how the base pairing works A's with teas and sees with cheese. And so if we take a look at our image down below, of course, over here, on the right hand side, we're showing you the images of James Watson and Francis Crick, who again, we're able to use Rosalind Franklin's photo 51 along with other information that they knew to help reveal the structure of DNA as a double helix structure where there are two strands of nucleotides that air anti parallel with respect to each other and, of course, recall from our previous lesson videos when we first introduced DNA. That anti parallel is just referring to the fact that one strand will go five prime to three prime in one direction from left to right here, whereas the other strand would go five prime to three prime in the opposite direction. And that's why they're called anti parallel. And of course, this image over here is showing you how the Watson Crick base pairing works where all of the site of scenes or sees base pair with all the guanine Zorg es and all of the ad means or ace base pair with all of the thigh means or tease on opposite strains. And this blue backbone that you see here of the molecule represents a sugar phosphate backbone. And we'll get to talk a little bit more about the details off the DNA structure in our next lesson video. But for now, this here concludes our introduction to how the DNA structure was discovered, and we'll be able to get some practice as we move forward in our course, so I'll see you all in our next video.