transcription question

[NE2000]

In transcription of RNA from a DNA strand, does RNA polymerase do the role of seperating the annealed strands like what DNA helicase does in DNA replication or are they just simplifying the process? The reason I ask is I came across a question asking for the mechanism of transcription and the answer provided extends into detail about the role of DNA helicase in unwinding the strands.

Secondly, if they were to ask a question regarding the formation of mRNA, would you include post-transcriptional modification?

Thirdly, on a non-transcription related note, is it right to say bacterial chromosomes lack a centromere while eukaryotes have one?

[ryley]

First: I think it is DNA helicase that seperates the strands in transcription, as I've never heard of RNA polymerase being able to do such a thing.

Second: Yes, its probably a good idea to mention removal of introns etc, but it would be worth clarifying with some of the past examiners reports to see if this is what vcaa wants in a response.

Third: Yeah, I'm pretty sure that bacterial chromosomes lack centromeres, but for more information regarding division of bacteria, have a look at this: http://staff.jccc.net/pdecell/celldivision/prokaryotes.html

I'd appreciate it if someone could confirm/correct anything I've said.

[shinny]

1. I remember having this same problem and I vaguely recall researching that RNA polymerase does this...but yeh, don't trust me on it. Check wiki or something perhaps.
2. I'd add a small sentence on it, even if its not very specific (e.g. The pre-mRNA is then sent to (some place; can't remember where) to be modified into mRNA) to save yourself some words.
3. I thought bacterial chromosomes were circular? Hence yeh, they wouldn't really have a centromere. I think its a good idea to learn the 3 or so key differences between prokaryote and eukaryote chromosomes because I remember doing so myself, but the thing is I really can't remember what these are =P 1 year of spesh and chem has pushed out all the bio as you can see from my answers @_@

[NE2000]

Thanks

If they ask chromosomal differnences would they be wanting physical differences in appearance (eg. no centromere vs. centromere, circular vs. linear) or would they accept major differences in the DNA (eg. introns vs. no introns, operons vs. no operons)

[shinny]

Well...both? The main ones that come to mind are circular vs linear, paired vs non paired and introns vs no introns. I've never even heard of operons =P

[lacoste]

what are operons?? uni stuff

do you mean lac operon??

[Faraz]

Alright RNA polymerase have a role in creating the RNA strands in transcription

for the last question bacteria have a single chromosomes. The only form of DNA that they have is the plasmid which is that circular ring from gene technology chapters if you can recall to. Therefore Bacteria do not have centromiers since they only have one  single chromosomes.