00:01
Looking at a diagram shows a short fragment of a double -stranded dna molecule.
00:06
So you have two strands.
00:08
The top one is 3 ' at the left side and 5 ' on the right side.
00:15
And the bottom strand is the opposite orientation, 5 at the left side and 3 on the right.
00:21
So you have two potential promoters.
00:26
The first promoter is on the top strand from 5 to 3 read as tatta.
00:33
And the second promoter is on the bottom strand from 5 to 3 read as agtat.
00:42
So first of all, in the eukaryotic gene, the promoter is the binding site 4.
00:51
So to answer the question, the promoter is the binding site of the rna polymerase c.
01:02
And before the polymerase can bind to the promoter region, obviously there are very important proteins.
01:10
We call it transcription factor.
01:13
And one of the subunits is called sigma fragment factor.
01:18
So the promoter is actually the binding site for the transcription factor, sigma factor.
01:25
And then the transcription factor will recruit the rna polymerase, which will also bind to the promoter region.
01:31
So to summarize it, say if you have a promoter region, p.
01:41
So first of all, you have proteins called transcription factor.
01:54
And one of them is sigma.
01:55
And once the transcription factor recognize the promoter region, they will actually recruit the rna polymerase to dock on it.
02:16
Rna polymerase is the enzyme that actually does the transcription.
02:22
So the correct answer is going to be c, d, both a and c.
02:54
The second part, in the diagram, which promoter is used? so you can see the arrow on the top line show you the transcription star site and the direction of transcription.
03:09
So you can see that transcription goes from left to right.
03:15
So the mrna that being made is from five to three direction.
03:23
So from there, we can tell that the top strand here is the template because the mrna is complementary to the template strand of dna.
03:36
And it has also opposite orientation.
03:39
And the bottom strand here has the same direction or orientation as the mrna and also providing the coding information.
03:46
So we call it coding strand.
03:49
So from there, you can tell that promoter number one is upstream of the mrna.
03:55
So promoter number one is the actual promoter that is being used.
04:00
And as you can see, the coding strand have promoter number two.
04:08
So you can see that this is at the downstream of the transcription initiation site.
04:16
So not number two.
04:27
Promoter one is, we call upstream, which is before the transcription initiation site.
04:39
So this is templates.
04:39
This is where the rna polymerase and transcription factor bind...