The Human Telomere
Robert R. Moyzis
Scientific American
August 1991, Vol. 265, Number 2, pp. 48-55.
Chromosomes are the thread-like components of the
cell nucleus that are responsible for heredity. They consist of the hereditary molecules, DNA and RNA, attached to a protein core. Segments of DNA that specify linear
sequences of
amino acids that subsequently, in the correct chemical environment, then fold into three dimensional conformations called proteins, are called genes. (Note: Varying linear sequences of amino acids specified by different
genes may nonetheless fold into essentially the same configuration and therefore protein since the functional properties of proteins repose on their three-dimensional configuration.) It is through proteins, because proteins are vital to all life processes (e.g. as enzymes, they regulate the so-called biochemistry co-extensive life), that genes are able to make their importance felt.
Not all segments of DNA in the chromosome, however, code for amino acid sequences. Among these nongenic sequences of DNA are those terminal sequences at each end of the chromosome. These were termed
telomeres by the Nobel laureate, Hermann J. Muller, even before the famous double-helix structure of DNA was disclosed. Furthermore, Muller opined, presciently (it turns out), that the telomere plays a vital role in cell welfare. What this role was remained unclear for some time because the precise structure of the telomere resisted disclosure.
This state of ignorance about the telomere structure finally began to lift in the 1980s due to techniques developed by Robert Moyzis and his colleagues at Los Alamos National Laboratory in the US. Partly as a result of this work, it has come to be appreciated, as Muller had suggested of the telomere, that nongenic portions of DNA can, nonetheless, still play crucial roles in cellular metabolism.
In the case of the telomere itself, the prevailing facts imply that the telomeres play a role in preventing the progressive degradation, during cellular replication of germ or reproductive cells at least, of the DNA in the chromosome. Otherwise, as in the case of the somatic or nonreproductive cells of the body where telomeres do progressively grow shorter with each cellular replication, we would not have the maintenance of species lines but rather eventual cell decay—and by extension, species extinction.
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