Telomerase activity is expressed in

Telomeres are sho repeated sequences of DNA present at the ends of linear chromosomes that are impoant for ensuring the complete replication of chromosome ends and for protecting the ends from fusion and degradation. When somatic cells replicate, a small section of the telomere is not duplicated and telomeres become progressively shoened. As the telomeres become shoer, the ends of chromosomes cannot be protected and areseen as broken DNA, which signals cell cycle arrest. Telomere length is maintained by nucleotide addition mediated by an enzyme called telomerase. Telomerase is a specialized RNA-protein complex that uses its own RNA as a template for adding nucleotides to the ends of chromosomes. Telomerase activity is expressed in germ cells and is present at low levels in stem cells, but it is absent in most somatic tissues.Ref: Robbins and Cotran Pathologic Basis of Disease; 9th edition; Chapter 2; Cellular aging; Page no: 67