Nurturing Life Sciences
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#Unit 3. Fundamental Processes
Telomerase, a reverse transcriptase that contains an RNA template, repeatedly adds TTAGGG repeats
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Embryonic cells, germ-line cells, and stem cells produce telomerase, but most human somatic cells produce only a small amount of telomerase as they enter S phase.
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As a result of their modest telomerase activity, their telomeres shorten with each cell cycle.
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Extensive shortening of telomeres is recognized by the cell as a double-strand break and consequently triggers cell cycle arrest and apoptosis.
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In mammals, six telomeric proteins (TRF1, TRF2, Rap1, TIN2, TPP1, and POT1) comprise a complex called shelterin
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Duplex telomeric DNA interactions of TRF1 and TRF2 and the binding of POT1 to the single-stranded TTAGGG repeats.