Telomerase

Telomerase is an enzyme that adds specific DNA sequence repeats ("TTAGGG" in all vertebrates) to the 3' ("three prime") end of DNA strands in the telomere regions, which are found at the ends of eukaryotic chromosomes. The telomeres contain condensed DNA material, giving stability to the chromosomes. The enzyme is a reverse transcriptase that carries its own RNA molecule, which is used as a template when it elongates telomeres, which are shortened after each replication cycle. Telomerase was discovered by Carol W. Greider in 1984.
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Telomerase /telo·mer·ase/ a DNA polymerase involved in the formation of telomeres and the maintenance of telomere sequences during replication. [more]Telomerase - Community and Resources

Noun
1. an enzyme in eukaryotic cells that can add telomeres to the ends of chromosomes after they divide
(hypernym) enzyme

A reverse transcriptase containing an RNA molecule that functions as the template for the tandem repeat at telomere. It synthesizes telomere to maintain its length after each cell division. It is active in embryonic cells and gametes, inactive in differentiated somatic cells, and reactivated in malignant cells. Telomerase can add one base at a time to the telomeric end of a chromosome. This maintenance work is required for cells to escape from replicative senescence.

an enzyme that directs replication of telomeres at the end of DNA strands; a reverse transcriptase that carries its own RNA template; inactive in regular cells, but active in cancerous cells.