Easy DNA Question - End Structure (Jun/04/2005 )

BismillahirRahmanirRahim

Hi all -- this should be a super-easy question. What do the ends of DNA look like? Is DNA composed of 2 interwoven strands like 2 strings that just end at the top and bottom, or are the ends connected in some way? Any links to a tutorial or graphics would be soooo helpful. Thanks so much!!!!

ali

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Hey I coldnt get what ur question was and not even that first line..!

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Do you mean the ends of chromosomes or the end of PCR products etc? Chromosomes are capped by something called telomeres, which are bound by several different proteins and also form a structure called a T-loop.

Telomeres prevent chromosomes ends from being recognised as DNA damage, and therefore being 'repaired' by the cell and joined to other chromosomes. If this happen it's disasterous for a cell when it divides and the chromosomes try to pull apart.

Telomeres are basically a simple repeat sequence, and in most cells, this number of repeats gets shorter with each cell division, leading to cells having a certain replication lifespan. In some cells, an enzyme called telomerase adds on more repeat units to the end to stabilise them (making the cell immortal), and in some specific a recombination process can extend them/maintain them without telomerase.

This web page might help. Shay and Wright are leaders in the telomere/telomerase field.
http://www.swmed.edu/home_pages/cellbio/shay-wright/

Regards,
Kirsty

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