Telomeres are end parts of linear Eukaryotic chromosomes. Telomeres are made up of thousands of repetitive TTAGGG nucleotides. One linear eukaryotic chromosome has telomeres at each end.
In human 46 chromosomes are present, therefore 92 telomeres are present in a single cell.
Telomeres as of now do not contain any coding part of the Gene but telomeres play very important role in protecting the structure of the chromosomes. Telomeres avoid the chromosome fusion and thus genomic instability.
DNA replicates by unwinding using specific enzymes like DNA polymerase, single strand binding protein, Helicase and many more. But these enzymes cannot replicate full length of DNA. As a result DNA length decreases after each cell division. Specifically after each cell division length of telomeres reduces.
Scientists have found co-relation between length of telomeres and cell division. They say that our body cells stop replicating when the length of telomeres becomes too short. Scientists have noticed that telomeres reaches its critical limit by 50 cell divisions, this limit is also known as Hayflick limit.
Cell death or aging:
Length of Telomeres can be used to determine the age of a cell. When length of telomeres reaches Hayflick limit cells receive a signal for cell senescence also known as cell death. Ageing is nothing but cell death. This is also known as cellular ageing.
Scientists have discovered that enzyme telomerase has the ability to add telomeric length by adding TTAGGG nucleotides in telomeric region of a cell. By this cellular aging can be bypassed or put on hold and also immortal (normal) cell can be converted to mortal cell.
Telomerase is a reverse tran script ase ribonucleoprotein enzyme complex. In a normal human body telomerase are genetically active only in some cells like stem cell, epidermal cell, hair follicular cell, white blood cells. So these cells have the capacity to divide more than 50 cell cycles.
Now scientists are hoping that aging and age-related problems can be answered by activating Telomerase gene which is present in Human chromosome3, the p arm (short arm), and locus 21.
Telomerase gene is also active in cancer cells so they can replicate many times that is they are immortal cells. But in normal cells telomerase are absent. Therefore, Telomerase can be used as marker in cancer diagnosis.
Scientists are hoping to find cure for cancer by inactivating telomerase gene by target therapy.
Anti-Telomerase therapy for cancer cells will be more specific, effective and efficient than the traditional chemotherapy.
As in traditional chemotherapy healthy cells are being affected or killed by the drug.
But Anti-telomerase therapy will target and stop the expression of Telomerase gene this in turn will stop replication of the telomeres. Due to this cancerous cells will become mortal and we can cure the cancer.
Future challenges are:
1, To understand how telomerase enzyme and its complex protein interact together to maintain telomeres length.
2. To intervene all this process in Cancer diagnosis and treatment.
3. To fully utilize all our knowledge in telomeres biology to treat age related problems.
4. To intervene aging process.
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