<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 . Its name is derived from the Greek nouns telos (τέλος) "end" and merοs (μέρος, root: μερ -) "part". For vertebrates, the sequence of nucleotides in telomeres is TT A GGG, with the complementary DNA strand being AATCCC, with a single - stranded TTAGGG overhang . This sequence of TTAGGG is repeated approximately 2,500 times in humans . In humans, average telomere length declines from about 11 kilobases at birth to less than 4 kilobases in old age, with the average rate of decline being greater in men than in women . </P> <P> During chromosome replication, the enzymes that duplicate DNA cannot continue their duplication all the way to the end of a chromosome, so in each duplication the end of the chromosome is shortened (this is because the synthesis of Okazaki fragments requires RNA primers attaching ahead on the lagging strand). The telomeres are disposable buffers at the ends of chromosomes which are truncated during cell division; their presence protects the genes before them on the chromosome from being truncated instead . The telomeres themselves are protected by a complex of shelterin proteins, as well as by the RNA that telomeric DNA encodes (TERRA). </P>

Where are telomeres located in a normal chromosome