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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.
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 .
They then used α factor to block cells with induced short telomeres in late G1 phase and measured the change in telomere length when the cells were released under a variety of conditions. They found that when the cells were released and concurrently treated with nocodazole , a G2/M phase cell cycle inhibitor, telomere length increased for the ...
In this example, the length of the chromosome has increased slightly during DNA synthesis; normally, telomeres are maintained at a constant length by complex regulatory mechanisms. In some cells, telomerase is absent and telomeres gradually shorten with each cell division. [1]
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]
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.
The pattern of bands are numbered on each arm of the chromosome from the centromere to the telomere. This numbering system allows any band on the chromosome to be identified and described precisely. [4] The reverse of G‑bands is obtained in R‑banding.
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 ...