00:03
This question is regarding the dna replication enzyme with the description.
00:10
So first of all, let's take a look at a description.
00:14
So put in short, complementary rna primer.
00:19
So before dna can be replicated, you have a template dna.
00:23
The template dna must have primer first because dna polymerase is not able to start a new strand.
00:35
So you must have, first of all, primers, which are mrna, short complementary mrna to bind to the dna template first.
00:47
And then from there, the dna polymerase is able to extend a new strand.
00:53
So as you can see, the red part is the rna primer.
00:57
So this is the very first step because the rna primer will need to bind to the dna template first before dna polymerase can extend the new dna strand.
01:12
And the rna primers are being put down by a particular enzyme we call primase.
01:21
Primase is enzyme that produce rna primer that are complementary to dna template.
01:27
So this actually is a first question.
01:30
Second, which enzyme break the hydrogen bond, bond the base pair? so before rna primer can be put down and by the primase and bind to the dna template, you originally have dna strand that are forming double helix structure.
01:50
Now, for replication to happen, you'll need an enzyme to open up this double helix structure to form a replication bubble.
01:57
So during the formation of replication bubble, the hydrogen bond between the nucleo, like the nitrogen base are being broken down.
02:18
As you can see that all these bars are hydrogen bond.
02:23
So these hydrogen bond are being broken by this enzyme we called helicase.
02:39
Helicase open up the replication bubble by breaking the hydrogen bond between the base pair so that now you can see that there is a bubble over there and the primer is able to find a dna template and bind to the template.
02:54
So that's the second description.
02:56
Third, which enzyme add complementary dna nucleotide to growing dna strand? so for the third case, basically it's the same as the first one.
03:12
You can see that first of all, you have double strand of dna replication bubble open by helicase and then you have primer that bind to the template by primase.
03:25
And once the primer binds, now you have a primer to begin with.
03:34
The rna polymer, dna polymerase is able to extend the, let's draw it this way, newly growing dna strand so that by putting the new nucleotide to the 3 ' end of the primer.
03:52
So this enzyme is the dna polymerase 3.
03:56
Dna polymerase 3 is also the primary polymerase.
04:08
So as you can see, once the primers bind to the template and you have an existing 3 ' end, the dna polymerase is able to extend the new dna strand from the 3 ' end of the primer.
04:23
So the dntp, our nucleotide, are being added to the 3 ' end, which is a growing dna strand.
04:30
So the third enzyme that does this job is dna polymerase number 3, 4...