TELOMERE FUNCTIONS - A REVIEW

Telomers are structurally and functionally complex. They consist of an array of simple DNA repeals at the extreme end of the chromosome, wit h a more complex array of repeats adjacent to it. A large number of pr oteins have been identified that bind to the telomeric DNA repeats or to the protein complexes that are-built at the chromosome end, Telomer es rend reform associations with each other. These associations have b een implicated in the formation of nuclear domains that may be importa nt for transcriptional regulation, for sister chromatid pairing at mit osis, and for homologous meiotic synapsis. Telomeric chromosome ends d o not cause delays in cell cycle progression, nor are they subject to DNA repair as are broken chromosome ends, Telomeres also provide a sep arate mechanism for adding additional copies of the telomeric DNA to c hromosome ends, This is needed to counterbalance tile loss of DNA sequ ences from chromosome ends due to incomplete DNA replication. The comp onents that participate in the latter mechanism and this process have been characterized in detail; the other functions of telomeres are les s well understood but are the subjects of active investigation.