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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 ...
A telomere (/ ˈ t ɛ l ə m ɪər, ˈ t iː l ə-/; from Ancient Greek τέλος (télos) 'end' and μέρος (méros) 'part') is a region of repetitive nucleotide sequences associated with specialized proteins at the ends of linear chromosomes (see Sequences). Telomeres are a widespread genetic feature most commonly found in eukaryotes.
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.
In adults, telomerase is highly expressed only in cells that need to divide regularly, especially in male sperm cells, [29] but also in epidermal cells, [30] in activated T cell [31] and B cell [32] lymphocytes, as well as in certain adult stem cells, but in the great majority of cases somatic cells do not express telomerase. [33]
The end replication problem is handled in eukaryotic cells by telomere regions and telomerase. Telomeres extend the 3' end of the parental chromosome beyond the 5' end of the daughter strand. This single-stranded DNA structure can act as an origin of replication that recruits telomerase.
Alternative Lengthening of Telomeres (also known as "ALT") is a telomerase-independent mechanism by which cancer cells avoid the degradation of telomeres.. At each end of the chromosomes of most eukaryotic cells, there is a telomere: a region of repetitive nucleotide sequences which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes.
When that chromosome subsequently replicates it forms two sister chromatids which both lack a telomere. [4] Since telomeres appear at the end of chromatids, and function to prevent their ends from fusing with other chromatids, the lack of a telomere on these two sister chromatids causes them to fuse with one another.
Alexey Matveyevich Olovnikov (Russian: Алексей Матвеевич Оловников; 10 October 1936 – 6 December 2022) was a Russian biologist.Among other things, in 1971, he was the first to recognize the problem of telomere shortening, to predict the existence of telomerase, and to suggest the telomere hypothesis of aging and the relationship of telomeres to cancer.