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DNA replication?

Wed Jan 25, 2012 12:35 am

Hi could anyone please supply a step by step numerical breakdown of the processes involved in DNA replication? I mean I know some processes happen at the same time, but what's the general thrust of things?

It would be really helpful if I could see something in a step 1, step 2, step 3 step 4 etc. type format.

Wed Jan 25, 2012 12:01 pm

Hi could anyone please supply a step by step numerical breakdown of the processes involved in DNA replication? I mean I know some processes happen at the same time, but what's the general thrust of things?

It would be really helpful if I could see something in a step 1, step 2, step 3 step 4 etc. type format.

You see the problem is I've read about and watched loads of videos about each of the individual steps, but I'm having real trouble stitching it all together. Of particular confusion is in this video here: http://www.youtube.com/watch?v=SMtWvDbfHLo it shows the DNA molecule being copied into RNA first, presumably for later transcription back into DNA?

However in this (really very good) online tutorial, it shows DNA being copied directly through a process of sem-conservative replication. So which is it? Or is it both? If so at which points do these processes occur? Also the initial video shows RNA-polymerase appearing to 'race along' the DNA molecule and unzip it to create an RNA template? But surely the RNA molecule doesn't move at all (or at least very little?) Isn't it the DNA molecule that gets fed through the RNA polymerase, a bit like film being fed through and old style cinema film camera?

Wed Jan 25, 2012 12:45 pm

The RNA Pol produces only short RNA fragment called primer, which is essential for DNA Pol to start the polymerization, because it is not able to start de novo synthesis of DNA. DNA is only able to append nucleotides to some other chain.
Thus the order would be
1) unwinding DNA (helicase, topoisomerases, SSB proteins etc)
2) synthesis of primer (RNA Pol)
3) synthesis of DNA (DNA Pol)
4) removal of RNA and substitution by DNA (DNA Pol)
5) ligation of the two consecutive DNA strands (ligase)

Wed Jan 25, 2012 5:07 pm

OK thanks. I had it a bit muddled I think. DNA replication does exactly what it says on the tin, it replicates the entire DNA genome, which is copied into daughter cells during mitosis and cell division, RNA (or mRNA) copies shorter sequences of DNA into it's mRNA equivalent, and transports the products from the cell nucleus to the ribosomes in the cytoplasm and it's in it's constituent organelles (the rough ER and the Golgi) for further processing and later transcription into proteins, which are then exported from the cell for use within the organism at large.

That's kind of the order of events I was stabbing at, although it didn't really sink in until today.

Thu Jan 26, 2012 7:38 am

roughly it could be like that...

Re: DNA replication?

Thu Jan 26, 2012 12:47 pm

Yeah there's a fair bit of detail still to fill in, but as you say that is the approximate order of proceedings. Where are you from BTW are you Polish at all? Do you live in Europe, or have you migrated somewhere else? (Just curious.)

Thanks for being so helpful dude.

Thu Jan 26, 2012 12:49 pm

Oh I get it, you're from the Czech Republic. I thought you seemed a little Eastern European. ;)

Thu Jan 26, 2012 1:05 pm

you mean on my picture? :lol: We usually consider ourselves as Middle-Europeans ;)

Re: DNA replication?

Thu Jan 26, 2012 1:13 pm

No, the way you write is common to many ex-Soviet block Europeans. One common give away for Eastern European's is not knowing when to use 'the' appropriately. (Or forgetting to use it at all.) There are other clues too. But no worries, as your English is really very good, and your biology is clearly much better than mine - which is what matters most, lol.

Again thanks for your help.
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