Telomeres are segments of DNA at the ends of chromosomes, the twisted strands of DNA, bound by protein, that contain the genetic material of all plants and animals, including humans. Elizabeth H. Blackburn, PhD, professor of biochemistry and biophysics at University of California, San Francisco, has pioneered research on telomeres. She has discovered that, among their many crucial roles, telomeres are involved in the separation of paired chromosomes when cells grow and divide. Proper cell division is crucial for ensuring that the two offspring, or daughter, cells inherit the appropriate allotment of genes. Missing or extra copies of genes are often observed in cancer cells.
Normal cells contain one set of DNA. But studies by the Blackburn lab and others have shown that when telomeres are damaged, their chromosomes fuse together, which prevents a cell from dividing completely. When this occurs, the cell keeps growing, metabolizing and replicating its DNA, without ever successfully separating its nucleus, which contains the chromosomes. As a result, the cell builds up multiple copies of DNA, as seen in the multiple bright spots of stained DNA (figures A and B).
In 1985, Blackburn and her then PhD graduate student at UC Berkeley, Carol Greider, discovered a novel enzyme, telomerase, which creates telomeres. They demonstrated that when the telomerase gene is mutated, it creates damaged telomeres, which disrupt normal cell division.
