الفهرس 
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Abstract
Telomerase enzyme is a ribonucleoprotein that adds new DNA sequences to the terminal ends of chromosomes (the telomere). Thus, it can prevent the progressive shortening of telomere during multiple cell cycles. Telomerase activity is downregulated in non malignant somatic cells, but it is activated in most types of human cancer.
The main two components of telomerase enzyme are hTERT and hTERC. The catalytic subunit hTERT possesses reverse transcriptase activity, and the second component coding RNA is hTERC. It is found that hTERT is the rate-limiting step in regulation of telomerase activity.