in this video, we're going to begin our lesson on DNA prelim races. And so it turns out that the primary enzyme that's responsible for building new DNA strands are actually these DNA prelim races. And you can actually see the function of this enzyme here in its name. And so you can see that anything that ends in A S E is going to be an enzyme, as we discussed in our previous lesson videos when we first introduced enzymes. And so these are gonna be enzymes that prelim arise or build d n A. And so DNA polymerase. Is there gonna be the primary ends? I'm responsible for building new strands of DNA. Now, organisms tend to contain multiple types of DNA prelim races, and these different types of DNA prelim races will have slightly different functions and moving forward. We're not going to talk about all of the different types of DNA prelim races were on. Lee going to focus on the most important DNA polymerase is involved directly with DNA replication. Now, new DNA strands that are built by these DNA prelim races are always going to be built in the same direction from the five prime end of the DNA molecule to the three prime end of the DNA molecule. And so these DNA, new DNA strands always being built from their five prime into the three prime and or direction eyes going to be something that's consistent with all DNA Polymerase is. And so the new DNA strands are always going to be elongating from its free three prime hydroxyl group, or O H group. And so recall from our previous awesome videos that the three prime end of the DNA strands has the free hydroxyl group, or O H group. And that is what's required to elongate the DNA strand. And we'll talk Maura about this requirement in our next lesson video. And so what you'll notice is down below. Over here, we're showing you this image, and this image is basically a little cartoon to help you remember that DNA. New DNA strands are always elongated from five prime to three prime. And so notice that this guy over here is the boss and he's saying, Hey, Polly or polyamorous, can you work an extra shift today? And the worker over here? The DNA polymerase, the saying boss, you know, I only work from five prime to three prime. I don't work any other shifts. And so hopefully this little, uh, creative image here can help you remember that new DNA strands are always built from five prime to three prime and never in the opposite direction from three prime to five prime. And so to remind you, a little bit of DNA structure here, remember, the DNA structure consists of these two strands of nucleotides that are anti parallel with with respect to each other. They go in opposite directions in terms of their five prime and three prime ends. And so notice that the five prime end is gonna have a free phosphate group for each of them on the three prime end has the free hydroxyl group, and it's the free hydroxyl group that is required to elongate new DNA strands. And so the new DNA strands can Onley be built in this direction from five prime to three prime. And so this year concludes our brief introduction to DNA prelim races and will continue to talk Maura about DNA prelim races and their requirements as we move forward in our course. So I'll see you all in our next video
DNA Polymerases Requirements
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in this video, we're going to talk about some DNA proliferates requirements. And so, in pro carry attic organisms, we know that there are multiple DNA prelim, a races that can have slightly different functions from our previous lesson videos. And we're not going to talk about all of the different types of DNA prelim races. But what you should know is that in pro Kerasiotes, it's specifically DNA. Preliminaries three written with a Roman numeral three is actually the primary enzyme that's responsible for elongating or building new DNA strands. And so notice in our image down below. Here, we're showing you DNA proliferates three. Now it turns out that all DNA prelim A races have to central requirements that air necessary for them toe operate. And we've got these two central requirements listed down below number one and number two right here. And so the first central requirement that's required for all DNA polymerase is is a template. All DNA prelim races require a template, and the template is really just referring to the old or parental DNA strand that's going to act as a guide for building the new strands. And so if you take a look at our image down below. Notice that the template strand is this strain that's down below right here. This is the old DNA template strand. And so all DNA prelim races require a template in order to, uh, know what DNA strand they should be building now, The second requirement that all DNA polymerase is require is a primer. Now, a primer is really just a small Arna molecule that acts as the starting point for DNA. Pola Marie's and so DNA polymerase requires a free three prime hydroxy group. And can Onley extend existing strands, it cannot actually build brand new DNA molecules from scratch. It requires again number one a template, and it requires a primer as a starting point so that it can provide the free three prime hydroxyl group that's needed for DNA polymerase to elongate or extend the new DNA strand. Now the primer is going to be built by the enzyme prime ace, and so primates is going to be the enzyme that builds the RNA primer. And so when we take a look at our image down below, notice that we're showing you the primates enzyme up here, and its job is to build this primer. This Arna primer and the Arnie primer acts as a starting point for DNA polymerase three. And so that's because the Arna primer is going to provide a free three prime hydroxyl group. And this free three prime hydroxyl group is what's needed for DNA polymerase three to extend the Strand. And, of course, as it extends the strand in this direction, uh, it's going to be base pairing these free nucleotides that come in with the template strand. And that is how it knows what nucleotide should go in which place in which order. Now, ultimately, this Arna primer that's in this molecule is going to be replaced. The ultimately the primary is gonna be converted to DNA. Um, and the DNA will be part of the newly built DNA strand, and we'll talk more about this a little bit later. But the enzyme that replaces or converts the RNA to DNA is going to be DNA proliferates. One a different DNA preliminaries. And so again, we'll talk Maura about that a little bit later in our course. But for now, this year concludes our lesson on DNA polymerase requirements. That DNA polymerase three is the primary enzyme that builds these new DNA strands, and it has to central requirements. It requires a template strand, and it requires a primer so that the primer provides the starting point for it to elongate the new DNA strand. And so we'll be able to get some practice applying these concepts and learn Maura Maura about DNA replication as we move forward in our course, So I'll see you all in our next video.
If the sequence of the 5'-3' strand is AATGCTAC, the complementary sequence has the following sequence:
DNA Polymerase Distinguishes Template from New Strand via Methylation
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in this video, we're going to talk about the ability for D. N. A polymerase to distinguish the old template D. N. A strand from the newly built D. N. A strand via methylation. And so over time add meaning and cytosine bases specifically on the old D. N. A strands. Or the template DNA strands are methylated via regulatory processes within the cell. Now methylation refers to the addition of a metal group, which is a specific type of functional group characterized by a C. H. 31 carbon and three hydrogen. Now, during DNA replication, the D. N. A polymerase has the ability to distinguish the old template D. N. A strands from the newly built strand. And the reason that the D. N. A polymerase can distinguish these two strands is because the template D. N. A strand, the old template DNA strand is methylated. Whereas the newly built strand is actually not yet methylated but it will become methylated once again over time. And so if we take a look at our image down below, we can get a better understanding of how methylation is important during DNA replication. And so notice on the left hand side we're showing you the original DNA molecule where there are two old template D. N. A strands and notice that each of these old template DNA strands is methylated specifically at cytosine and adenine residues uh really only citizen and editing residues are going to be the ones that are most likely to become methylated and there's methyl groups on the opposite strand as well. And so each of these little pink circles that you see represents metal groups. Now in the process of DNA replication, we know that these two D. N. A template strands are going to be separated and they're each going to serve as a template for building a brand new strand. Now, once again the old template D. N. A. Strand is going to be methylated. However the newly built D. N. A. Strand is not yet going to be methylated. So we could say that it is not methylated yet. And so the D. N. A polymerase has that ability to be able to distinguish the newly built D. N. A strand from the old template DNA strand just by this methylation process. And so this is going to be important later down the line as we start to continue moving forward and talking more about the abilities of the D. N. A. Preliminaries. But for now this here concludes our brief lesson on how the D. N. A polymerase has the ability to distinguish the old template D. N. A strand from the newly built strand. And it does so via methylation because the template strand is going to be methylated. But the new strand will not yet be methylated. And so we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video
What is DNA methylation?
The addition of ethyl groups (-CH2-CH3) to the sugar-phosphate backbone of DNA.
The addition of ethyl groups (-CH2-CH3) to the adenine and cytosine bases of DNA.
The addition of methyl groups (-CH3) to the sugar-phosphate backbone of DNA.
The addition of methyl groups (-CH3) to the adenine and cytosine bases of DNA.
Why is DNA methylation important in DNA replication?
Methyl groups bind to and stop the replication of genes that the cell does not need.
Methyl groups bind to and increase the replication of genes that the cell needs.
Methyl groups bind to the old DNA strands so DNA polymerase can recognize the new DNA strands.
Methyl groups bind to the new DNA strands so DNA polymerase can recognize the old DNA strands.