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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.
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 ...
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]
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.
Repeated sequences (also known as repetitive elements, repeating units or repeats) are short or long patterns that occur in multiple copies throughout the genome.In many organisms, a significant fraction of the genomic DNA is repetitive, with over two-thirds of the sequence consisting of repetitive elements in humans. [1]
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.
Telomerase is a ribonucleotide protein that helps repair and replace degraded telomeres. However, telomerase fails us as we age; it becomes less able to repair telomeres, and our whole body starts falling apart. This means that our cells can no longer divide or divide with errors, and some believe that this contributes to the process of aging.