Clarifications on Telmeres

[aznnytezx]

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So, I am reviewing for biology before starting several practice problems.

Can anyone explain to about the two problems that replication reaches at the end of DNA strands? Thanks !

 

[Xo1991]

Yeah I gotchu.

Well you know in DNA replication the new strand is synthesized by DNA Pol III in prokaryotes and is initiated by an RNA primer since DNA Pol starts by adding nucleotides to the 3' end of an already existing strand.

But the lagging strand needs a lot of RNA primers since it's going in the direction opposite to the replication fork (but remember DNA pol is still adding 5' to 3' even on the lagging strand).

So when it gets to the end of the lagging strand, there isn't enough room at the end of the 3' end to put down the RNA primer, so what happens is the enzyme Telomerase extends the 3' end so that there is enough room to add an RNA primer. That extension is also called a telomere.

 

[Piepiesuperpie]

http://www.youtube.com/watch?v=AJNoTmWsE0s

Here is a video/visual explanation of what azn said. Hope it helps 🙂