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Critically short telomeres trigger a DNA damage response and cellular senescence. [32] Mice have much longer telomeres, but a greatly accelerated telomere shortening-rate and greatly reduced lifespan compared to humans and elephants. [33] Telomere shortening is associated with aging, mortality, and aging-related diseases in experimental animals.
Resolving the question of why cancer cells have short telomeres led to the development of a two-stage model for how cancer cells subvert telomeric regulation of the cell cycle. First, the DNA damage checkpoint must be inactivated to allow cells to continue dividing even when telomeres pass the critical length threshold.
When the cell does this due to telomere-shortening, the ends of different chromosomes can be attached to each other. This solves the problem of lacking telomeres, but during cell division anaphase, the fused chromosomes are randomly ripped apart, causing many mutations and chromosomal abnormalities. As this process continues, the cell's genome ...
Telomeres at the end of a chromosome. The relationship between telomeres and longevity and changing the length of telomeres is one of the new fields of research on increasing human lifespan and even human immortality. [1] [2] Telomeres are sequences at the ends of chromosomes that shorten with each cell division and determine the lifespan of ...
Telomeres are DNA tandem repeats at the end of chromosomes that shorten during each cycle of cell division. [27] Recently, the role of telomeres in cellular senescence has aroused general interest, especially with a view to the possible genetically adverse effects of cloning .
The telomeric region of DNA does not code for any protein; it is simply a repeated code on the end region of linear eukaryotic chromosomes. After many divisions, the telomeres reach a critical length and the cell becomes senescent. It is at this point that a cell has reached its Hayflick limit. [12] [13]
This results in the two daughter cells receiving an uneven chromatid. [4] Since the two resulting chromatids lack telomeres, when they replicate the BFB cycle will repeat, and will continue every subsequent cell division until those chromatids receive a telomere, usually from a different chromatid through the process of translocation .
DNA quadruplex formed by telomere repeats. The looped conformation of the DNA backbone is very different from the typical DNA helix. The green spheres in the center represent potassium ions. [62] At the ends of the linear chromosomes are specialized regions of DNA called telomeres.