Bacterial DNA replication (Circular)

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Bacterial DNA replication (Circular)

Post by poncecernesto » Tue Apr 11, 2017 7:03 pm

Firstly, do prokaryotic bacteria only replicate with circular DNA? or is that just some and maybe specific structures within the prokaryotic bacteria.

I'm gonna try to explain what I know, and if anyone could correct me (I'm very bad with circular replication), that would be great.
Also, could someone explain to me the directionality of the replicated strands within the circular chromosome?

So, from what I know, theres the ori, which I think since the circular chromosome is still two strands in a double helix, there's one ori on each strand right? Then DNA Pol appears and begins to replicate one strand after they have been unwound, making bubble, but because there's two ori, there's also two DNA pol going to each direction. Once both reach the other side of the ori, they arrive at a ter-tus complex that somehow separates the strands from the originals and makes a copy of the circular chromosome.

As you can read I have a pretty basic understanding of this, so if someone could explain to me how it works in a relatively simple fashion that would be much appreciated, especially how ter-tus leads to termination.

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Re: Bacterial DNA replication (Circular)

Post by claudepa » Tue Apr 18, 2017 9:49 am

DNA pol is a complex of many proteins. Some of them: DNA A, DNA B, pol1, pol2, pol3. primase. pol1 was the first to be discovered by Arthur Kornberg. It is why it is called 1. But in fact the one which is synthetizing DNA at the replication forks is pol3. probably pol1 was more abondant and it is why it was discovered first. DNA A open the DNA at ORI making the buble and therefore creating the 2 replication forks. After primase has allowed the begining of synthesis by hybridizing primers (and therefore 3'OH extremities) at the 2 dissociated strands at ORI, there will be 2 helicases (1 for each fork) to dissociate the 2 strands of DNA and 2 pol3 (one at each fork) to synthetize the new strands.
If you wish more information you can look for Kornberg publications for pol and to Cairns publications for ORI. Kornberg got the Nobel prize, may be Cairns also but I am not certain.

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