DNA Replication

[nashaiy]

So for DNA replication, my EK book says that DNA is read 3' to 5' and synthesized 5' to 3'. This made sense until I read a random bio passage talking about operons where it said that the promoter for the operon was upstream from the gene coding and showed it as being before the gene coding region. If DNA is read 3' to 5', then shouldn't the promoter be closer to the 3' region and thus downstream from the gene coding region? I've seen this a couple of times now in descriptions of the operon, could someone please explain?

Also, as a side note, do we have to know the different types of DNA/RNA polymerases? They aren't mentioned in EK. If so, could someone give me a very brief couple of words about each one so I know I have them correct from my wikipedia look up? I would very much appreciate it. Thanks!

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[circulus vitios]

Promoters are used to promote transcription. They have no role in DNA replication.

 

[nashaiy]

Promoters are used to promote transcription. They have no role in DNA replication.

I apologize for the confusion. I meant transcription when I wrote the original post. The EK books say that transcription (just like replication) proceeds by the RNA polymerase reading from 3' to 5' and synthesizing from 5' to 3'. Thus, I still don't understand why the promoter, which is stated to come "before" the gene coding region, would be considered "upstream" as DNA is READ 3' to 5'. Wouldn't the promoter be "downstream" (i.e. closer to the 3' end of the DNA) than "upstream" in order for it to be before the gene coding region.

Thanks!

 

[circulus vitios]

I apologize for the confusion. I meant transcription when I wrote the original post. The EK books say that transcription (just like replication) proceeds by the RNA polymerase reading from 3' to 5' and synthesizing from 5' to 3'. Thus, I still don't understand why the promoter, which is stated to come "before" the gene coding region, would be considered "upstream" as DNA is READ 3' to 5'. Wouldn't the promoter be "downstream" (i.e. closer to the 3' end of the DNA) than "upstream" in order for it to be before the gene coding region.

Thanks!

Maybe these pictures will make it clearer:

Look at the bottom picture. The bottom DNA strand is being read in the 3'-to-5' direction and the RNA strand is being synthesized in the 5'-to-3' direction.

Now look at the top picture. Either of the strands on the left side can be 'upstream' or 'downstream,' but by left-to-right reading convention you would say that the promoter is 'upstream' of the coding region.