Sunday, July 17, 2011

PHYSIOLOGY TUTORIAL


Human aging can be stopped by adding telomerase: comment
We may think that, human aging can be stopped by adding telomerase but, telomerase causes cells to divide rapidly and uncontrollably. Such an excessive cellular proliferation may leads to cancerous growth. So you can’t expect telomerase to become the elixir of your youth.
At the ends of each chromosome is a non functional strand of DNA called telomere. It has been observed experimentally that telomeres shorten with each successive cell division. Shortened telomeres activate a mechanism that prevents further cell multiplication. When telomeres become too short, the cells die.
In 1965, Leonard Hay flick discovered the Hay flick limit-phenomenon-is a number of times a normal cell divide before the telomere reaches critical length.
Somatic cells can only divide around 30-50 times due to Hay flick effect. On the other hand germcells, stemcells and cancerous cells (considered immortal –in the sense that they can reproduce indefinitely) contain telomerase that prevents Hay flick limit. This enzyme extends the telomere of chromosome and prevents shortening of telomere.

2 comments:

Pragadesh Rajendran said...

Madam ,
Is this the telomerase that causes cancerous proliferation or how does it appear in cancerous cells ?

Dr.Vinodha said...

dear dr.pragadesh, In normal specialized cells,telomerase is turned off ,telomere shortens and the cells age.(follows Hay -flick).In cancer cells telomerase is turned back on.(ignoring Hay-flick and divide uncontrollably.(however telomerase alone is not enough to cause cancer many other things must go wrong)Mitoses in a cell depends on many factors like protein growth factors,transcription factors &signalling molecules.they are under genetic control&so the cell cycle.A mutation in a gene results in inappropriate mitoses.implicated genes encodes growth factors, transcription factors or telomerase.