Telomeres are short conserved random tandem repeats present at the end of human chromosomes and acts as Cap/Helmet on chromosome. Telomeres present on the top prevents nearby chromosomes from fusing with each other which otherwise can cause malfunction or cancer. Telomeres are made of repeating sequences of TTAGGG on one strand paired with AATCCC on the other strand. Thus, one section of telomere is a "repeat" made of six "base pairs. Human telomeres typically range between 10 to 15 kb. An enzyme named Telomerase adds bases to telomere after each cell division/cycle.
Telomerase prevents telomeres from degrading
excessively in developing cells. However, when cells divide repeatedly,
telomerase levels drop, causing the telomeres to shorten and the cells to age. Telomerase
remains active in sperm and eggs, which are transferred from one generation to
the next. Any organism with reproductive cells would soon become extinct if
telomerase was absent, as it keeps the telomeres long.
Capacity of a human cell to divide after which
they become senescent is Hayflick’s limit. Generally normal human cell
can divide 50-60 times and thus cannot store the cell lines for more than a
week. But in case of cancerous cell lines, there is seen increase in hayflick’s
limit as cancerous cells somehow maintains telomeres i.e. Cancer
cells maintains the length of teleomere and thus can be stored for longer time period.
As every coin has two sides, there are certain
cons of using cancerous cell lines for research i.e. the metabolism and
pathways cannot be sometimes translated to how it happens in normal human cell.
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