Hey, everyone. So in this video, we take a more detailed look at the DNA double helix. Now here we're going to say the DNA double helix has a width of 20 Ångströms. Remember, an Ångström is a capital A with that little circle over it. And we're going to say typically, we're going to have 10 base pairs per turn, and within a full turn, a length of approximately 34 Ångströms. So, if we took a look here, we would say that the width of this DNA double helix is 20 Ångströms. So that's from this distance to this distance. We said that the full length of a turn, which is composed of 10 base pairs – 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 – that's a full turn. Its length is 34 Ångströms.
Now, this full turn is made up of two types of grooves. We're going to say the helical shape of DNA creates two grooves that are present on the exterior of its two strands. We have first our major groove. This is the wider and steeper groove of the DNA double helix, and then we have our minor groove. This is going to be the less wide and more shallow groove. If we take a look here, look how deep this groove is. That is our major groove. And here, this one is not as deep, so this is our minor groove.
We're going to say, taking a look at both the major and minor grooves within a given turn adds up to this 34 Ångströms. But how much of it is composed of major groove and how much of it is composed of minor groove? Well, the major groove is about 22 Ångströms in terms of length, and then the remainder, which is about 12 Ångströms, belongs to the minor groove.
Now here we're going to say proteins can bind to these grooves in order to regulate RNA transcription and DNA replication. So when we're talking about proteins binding to DNA, if we're talking about medications that deal with affecting our DNA, they're typically binding to these grooves, the major and minor grooves, and affecting them, and then eliciting a different type of response within our genetic makeup. So just remember that when we're talking about a more detailed look at DNA, we have to take into consideration the width of the DNA double helix. We have to take a look at its length. And remember, in a given turn, which is made up of, on average, 10 base pairs, we're going to have an overall length composed of this major and minor groove.
