Different mechanisms of telomere length regulation

Eukaryotic chromosomes are linear and have their ends formed by DNA-protein structures, telomeres. At present more and more facts demonstrate the dive rsity of telomere functions. Telomeres protect the chromosome ends from deg radation, fusion, recombination, and from the repair system that recognizes nicks in DNA strands. As shown recently, shortening of the telomeres is a cause of cell aging. In most organisms, telomeres are elongated by means of a special ribonucleoprotein complex; however, in some insects this takes p lace by either gene conversion or transposition of mobile elements. Evoluti onary relations between different types of telomeres are discussed.