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<p>Elizabeth Blackburn (UCSF) Part 3: Stress, Telomeres and Telomerase in Humans</p>
<p>- A telomere is a region of repetitive nucleotide sequences at each end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes.</p>
<p>- sequence of nucleotides in telomeres is TTAGGG, with the complementary DNA strand being AATCCC, with a single-stranded TTAGGG overhang.</p>
<p>- In the early 1970s, Russian theorist Alexei Olovnikov first recognized that chromosomes could not completely replicate their ends. Building on this, and to accommodate Leonard Hayflick's idea of limited somatic cell division, Olovnikov suggested that DNA sequences are lost every time a cell/DNA replicates until the loss reaches a critical level, at which point cell division ends. and In 1975–1977, Elizabeth Blackburn who is preseter of this video, discovered the unusual nature of telomeres, with their simple repeated DNA sequences composing chromosome ends. In addition, Blackburn, Carol Greider, and Jack Szostak were awarded the 2009 Nobel Prize in Physiology or Medicine for the discovery of how chromosomes are protected by telomeres and the enzyme telomerase.</p>
<p>- Telomeres shorten in part because of the end replication problem that is exhibited during DNA replication in eukaryotes only. Because DNA replication does not begin at either end of the DNA strand, but starts in the center, and considering that all known DNA polymerases move in the 5' to 3' direction, one finds a leading and a lagging strand on the DNA molecule being replicated.</p>
<p>- Telomerase is the natural enzyme that promotes telomere lengthening. It is active in stem cells, germ cells, hair follicles, and 90 percent of cancer cells, but its expression is low or absent in somatic cells. Telomerase functions by adding bases to the ends of the telomeres. Cells with sufficient telomerase activity are considered immortal in the sense that they can divide past the Hayflick limit without entering senescence or apoptosis. For this reason, telomerase is viewed as a potential target for anti-cancer drugs</p>
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<p>sSMS : http://seqll.com/wp-content/uploads/2016/09/helicos-true-single-molecule-sequencing-movie_2.mp4</p>
<p>cancer genomics : https://www.youtube.com/watch?v=q4Z-RO6t1tU</p>
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