DNA Replication

[Dark Horse]

Hey guys, I am really confused about DNA replication. I don't know which way the DNA is copied, and how do you know which strand is the lagging strand and which is the leading strand? An explanation of this process would be really handy, because I keep getting confused about whether it is 5' to 3' or 3' to 5'. Any help would be much appreciated

[Jdog]

firstly it is important to know that DNA replication ALWAYS occurs in a 5'-3' direction

Initially helicase unzips the complementary strands and DNA Gyrase makes these proteins that make sure they don't come back together again.,

the process of replication with the leading strand is relatively simple becuse there is a free 3' end.

DNA polymerase ( the enzyme used to put together the new chain) always needs a free 3' end to begin from so the leading strand has no problems.


The lagging strand however does not have this free OH ending, therefore the addition of RNA primers is required, From this intial RNA primer, DNA polymerase can synthesise. in the end the RNA primers get replaced with DNA fragments, and DNA ligase glues it all up. Okazaki fragments are the fragments of DNA whcih are synthesized from the start of the RNA primers,


What ive said is a bit simplistic but im sure thats all that needs to be known, maybe a few typos as well.

[Russ]

Jdog has most of it but just clarifying:

DNA gyrase doesn't "make" proteins, it relieves supercoiling to allow replication
RNA primers are required on both strands, not just the lagging strand

[Jdog]

whats the enzyme that makes those proteins that prevent the strands coming back together then/? I haven't done this stuff in a while forgotten the specifics.

[Jdog]

http://www.youtube.com/watch?v=teV62zrm2P0 this link might be helpful

[Russ]

Topoisomerase? What, single stranded binding proteins? I don't think they're enzymatically produced.

It all blurs after a couple of months