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Human chromosomes (grey) capped by telomeres (white). 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).
The presence of repeated sequence DNA makes it easier for areas of homology to align, thereby controlling when and where recombination occurs. In addition to playing an important role in recombination, tandem repeats also play important structural roles in the genome. For example, telomeres are composed mainly of tandem TTAGGG repeats. [15]
(A) Telomere-bound proteins involved in preventing the activation of the DNA damage response checkpoint and of DSB repair mechanisms in S. cerevisiae (top) and in humans (bottom). (B) Overview of the normal function of telomere-shelterin complexes and the pathways activated by telomere shortening. [5]
In molecular biology, [1] [2] [3] DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. [4] DNA replication occurs in all living organisms acting as the most essential part of biological inheritance .
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 ...
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 ...
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.
Sgo2 remains in subtelomeres, whose cells lack telomere DNA. Sgo2 represses the expression of subtelomeric genes that is in a different pass-way from the H3K9me3- Swi6-mediated heterochromatin. Sgo2 has also repressive effects for timing of subtelomeres replication by suppressing Sld3, [25] a replication factor, at the start of the replication ...