Normal human chromosomes have long G-rich telomeric overhangs at one end

摘要: Telomeres protect the ends of linear chromosomes from degradation and abnormal recombination events, in vertebrates may be important cellular senescence cancer. However, very little is known about structure human telomeres. In this report we purify telomeres analyze their termini. We show that following replication daughter have different terminal overhangs normal diploid telomerase-negative fibroblasts. Electron microscopy those long yields 200 ± 75 nucleotides single-stranded DNA. This overhang four times greater than amount telomere shortening per division found these cells. These results are consistent with models which leading-strand synthesis generates a blunt end while lagging-strand produces G-rich 3′ overhang, suggest variations regulate rate Our do not exclude possibility nuclease processing events leading strand result short on one end.