Senescence & telomeres
What kinds of organisms have senescence? What kinds of organisms have telomeres? Do these things always go together? If a cell has telomeres, does it have telomerase?
Senescence is found in complex life forms in organisms of certain taxonomic groups including animals and plants.
Most of the eukaryotic chromosomes contains repetitive sequences at their ends called telomeres. Since bacterial DNAs are circular and lack ends, they dont possess telomeres.
Senescence or ageing is related to telomere activity. With every cell division the telomere gets shorter. When it gets too short, the cell cannot divide any longer and becomes inactive and dies.
Telomerases help in adding telomere repeat sequence. These are found in normal stem cells and most cancer cells to overcome senescence. They are usually absent or present at very low levels in somatic cells.
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