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Telomere is a region of ... the sequence repeats are ... eventually running out after a certain number of cell divisions and resulting in the eventual loss of vital ...
Olovnikov proposed that every time a cell divides, a part of the DNA sequence is lost, and if this loss reaches a certain level, cell division will stop at the end. [ 7 ] [ 9 ] [ 16 ] According to his "marginotomy" theory, there are sequences at the end of the DNA (telomeres) that are placed in tandem repeats and create a buffer zone that ...
Telomerase, also called terminal transferase, [1] is a ribonucleoprotein that adds a species-dependent telomere repeat sequence to the 3' end of telomeres. A telomere is a region of repetitive sequences at each end of the chromosomes of most eukaryotes. Telomeres protect the end of the chromosome from DNA damage or from fusion with neighbouring ...
When telomeres reach a critically short length, sufficient shelterin proteins to inhibit checkpoint activation are not available, although NHEJ and HR generally remain inhibited at this point. [5] This loss of inhibition is one reason why telomere shortening causes senescence (Figure 1B).
[13] [44] Further evidence also shows a decrease in trimethylated histone H3K9 at the telomeres and loss of binding of the Shelerin-component TRF2 at the subtelomeres. [44] As a result, the increased TERRA expression further contributes to abnormal shorting of the telomere, leading to the spontaneous genomic instability and systemic ...
Loss of telomeric DNA through repeated cycles of cell division is associated with senescence or somatic cell aging. In contrast, germ line and cancer cells possess an enzyme, telomerase, which prevents telomere degradation and maintains telomere integrity, causing these types of cells to be very long-lived.
As the cell divides, the telomeres on the end of a linear chromosome get shorter. The telomeres will eventually no longer be present on the chromosome. This end stage is the concept that links the deterioration of telomeres to aging. Top: Primary mouse embryonic fibroblast cells (MEFs) before senescence. Spindle-shaped.
Shelterin (also called telosome) is a protein complex known to protect telomeres in many eukaryotes from DNA repair mechanisms, as well as to regulate telomerase activity. In mammals and other vertebrates, telomeric DNA consists of repeating double-stranded 5'-TTAGGG-3' (G-strand) sequences (2-15 kilobases in humans) along with the 3'-AATCCC-5' (C-strand) complement, ending with a 50-400 ...