Primer/Telomeres

[nothing123]

---

Members don't see this ad.

Hi,

My understanding is that during DNA transcription, the primer that is initially laid down to start elongation is eventually replaced by DNA through the action of DNA polymerase I. However, my TPR book now says that if the primer is laid down very close to the 5' end, it is not in fact replaced by DNA, which is one of the reasons telomeres exist. Can someone confirm this? Why would DNA polymerase I have trouble replacing the primer only if it's close to the 5' end?

Thanks.

 

[Bu2009]

K I will just type to you what I have from my genetics book since I'm no expert at this subject. This book is written by a prof at my university. "genetics a conceptual approach". I guess this will help me relearn this topic as well.

Anyways what i have here is that In linear chromosomes with multiple origins, the elongation of DNA in adjacent replicons also profvides a 3'-OH group preceding each primer. At the very end of a linear chromosome, however, there is no adjacent stretch of replicated DNA to provide this crucial 3'-OH group. When the primers at the end of the chromosome has been removed, it cannot be replaced with DNA nuclotides, which produces a gap at the end of the chromosome, suggesting that the chromosome should become progressively shorter with each round of replication. The chromosome would be shortened with each successive generation of an organism, leading to the eventual elimination of the entire telomere destablization of teh chromosome, and cell death. But chromosomes don't normally become shorter each generation and destablized. why?

Single stranded protruding end of the telomere can be extended by telomerase, (you should know what this does). An enzyme with both a protein and an RNA component. RNA is G-rich strand that pairs with the overhanding 3' end of DNA and provides a template for the synthesis of additional DNA copies of the repeaets. DNA nucleotides are added to the 3' end of the strand one at a time after several nucleotides have been added, the RNA template moves down the DNA and more nucleotides are added to the 3' end .. In this way telomerase can extend the 3' end of the chormosome without the use of a complementary DNA template. How teh complementary C-rich strand is synthesized is not yet clear.


There are various diagrams with this topic that I wish I could show u. but I hope this helps