1 Beginning of the End: Origins of the Telomere Concept

Abstract

Mitotic chromosomes, unless treated in special ways, appear as remarkably uniform and structureless rods, whose only differentiation is a bend or constriction where the spindle fibers attach. It is not surprising that classic cytologists paid little attention to the ends of these rods, or never even gave them a name until well into this century. The Drosophila geneticist Hermann J. Muller was one of the first to speak of telomeres, a word that itself tells us something of what he had in mind. Telomere means literally end-part, coming from the two Greek roots telos (end) and meros (part). Meros often carries the implication of segment, as in the metameres of an insect or worm, and so telomere suggests the terminal segment of a segmented structure. More importantly, telomere was coined on the model of centromere and chromomere, terms that were widely used in the 1930s and 1940s with mixed cytological and genetic connotations. Centromere was really a geneticist’s word. Although more or less synonymous with the cytologist’s spindle attachment region, or kinetochore, it carried decidedly theoretical implications, particularly the notion that a centromere was essential for the long-term stability of a chromosome. The centromere was also assumed to segregate reductionally at the first meiotic division, and it thereby provided a fixed point on the genetic map of organisms like fungi that had ordered tetrads. Chromomere could mean any of the small bumps along the length of an early prophase chromosome, but it too carried a genetic implication, namely, that the...