Antiparallel structure of DNA strands (video) | Khan Academy
They would be the same, because one side of the DNA would have adenine and the other thymine in the same place, and they can only link to. Specifically, adenine bases pair with thymine bases and guanine bases pair there is a linear relationship between the amount of guanine and cytosine in a. Oct 19, The other two are Uracil, which is RNA exclusive, and Thymine, which is DNA . Congratulations on making it through the whole guide!.
Oops, let me just draw all the phosphates ahead of time.
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So you have the phosphates on that end and then you have the sugars. And you see the same thing on the other strand as well. Where we have phosphate with a sugar then another phosphate then a sugar then another phosphate.
Let me circle the sugars as well. So we have a sugar there and then you have the sugar there as well. So on the other strand it's also going to look like this. So let me draw the phosphates. I'm just abstracting them now.
What is the Difference Between Purines and Pyrimidines?
So the phosphate and then you have the sugars in between the phosphates. And what links them, you can think of them as the rungs on the ladder. These are the complementary nitrogenous bases. And the reason why we call them nitrogenous bases, I actually forgot to talk about it in the last videos, is that these nitrogens are really electronegative and they can take up more hydrogen protons.
They have an extra lone pair. The nitrogens have an extra lone pair that can be used up under the right conditions to potentially sop up more hydrogen protons. Now, a lot of people ask, "Well, if you have these nitrogenous bases here, "why is DNA called an acid? And that's what actually forms the rungs of the ladder when these complimentary nitrogenous bases form these hydrogen bonds with each other.
But even more, the reason why we call it an acid is the phosphate groups, when they're protonated, are acids. Now the reason why we tend to draw them deprotonated is they're so acidic that if you put them in a neutral solution, they're going to be deprotonated.
So this is the form that you're more likely to find it in the nucleus of an actual cell. Once it's actually already deprotonated. But in general, phosphate groups are considered acidic. And if I were to draw kind of a more pure phosphate group, and I talked about this already in the last video, I would have it protonated and so I wouldn't draw that negative charge like that.
So that's just a review of last time. Since I already started abstracting it, let's abstract further.
DNA function & structure (with diagram) (article) | Khan Academy
So let's draw the nitrogenous bases a little bit. So I have thymine here.7 Things Men Want But Don't Ask For - Relationship Advice For Women by Mat Boggs
And I will do thymine in this green color. So this right over there is thymine. So this is attached to thymine.
And the complementary nitrogenous base to thymine is adenine. Which I will do-- Let's see I'm running out of colors here. I'll do this in an orange color since it's got so many nitrogens on it.
So actually should include that hydrogen right over there. So this right over here is adenine. Now they have these hydrogen bonds between them right over here. Because they have partially negative and positive charges on either end that are attracted to each other.
And then we go to this rung, one rung below it. And what is going on? Well, let's see we have-- Now I really am running out of colors here.
We have this nitrogenous base is cytosine. This nitrogenous base right over here is cytosine. This nitrogenous base here is cytosine. Because the bases are opposites two are purines and two are pyrimidines the purine bases want to bind with the pyrimidine bases. Therefore, thymine, a pyrimidine, will bind to adenine, a purine. When this occurs, there are two hydrogen bonds formed to completely stabilize the piece of the DNA ladder. If thymine was to bond with any other of the bases, this particular hydrogen bond wouldn't be formed correctly and the DNA ladder would have rungs crossing one another.
This would cause the ladder to bow in and out and would be ineffective for further use by the body. How Thymine Could Be a Problem Of course, everything comes with a potential problem, and thymine is no exception. From time to time, there will be an inadvertent mutation, or a strangely formed DNA structure.
In other words, one strand of DNA will always be an exact complement of the other as far as purines and pyrimidines go. This complementary pairing occurs because the respective sizes of the bases and because of the kinds of hydrogen bonds that are possible between them they pair more favorably with bases with which they can have the maximum amount of hydrogen bonds.
There are two main types of purine: One strategy that may help you remember this is to think of pyrimidines like pyramids that have sharp and pointy tops.
Which purines pair with which pyrimidines is always constant, as is the number of hydrogen bonds between them: C with three hydrogen bonds One way to remember which bases go together is to look at the shapes of the letters themselves. The letters made up of only straight lines A and T are paired with each other, while the letters that are made up of curves G and C also go together.