Helsinki Paper

Date:
1977
Reference:
PP/CRI/H/6/6
Catalogue details

Licence: In copyright

Credit: Helsinki Paper. Source: Wellcome Collection.

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    CHROMOSOME STRUCTURE - A POSTSCRIPT FRANCIS CRICK The Salk Institute for Biological Studies, P.O. Box 1809, San Diego, California 92112, U.S.A. The organisers have asked me, as an outsider from molecular and cell biology, to make a few retrospective comments on the very interesting and successful 6th International Chromosome Conference. My most general impression is that these meetings, which started as rather informal family gatherings, have (now that the attendance has grown) become somewhat isolated from the main stream of recent biologic al developments. Evolution, guided by natural selection, must always remain the grandest theme in biology, but if we are to arrive at a deep and quantitative knowledge of it we must understand developmental bi ology in far greater depth than we do now. To do this it is essential (among other things) for us to know exactly what constitutes a eukary- otic gene and how it acts. In prokaryotes we already know, in broad outline, the answers to these questions. It is one of the scandals of molecular biology that we still cannot answer them for eukaryotes. From this broader point of view the metaphase chromosome, which is the object of study of many of .the Conference members, is the dullest form of chromosome: an inert package needed to make orderly mitosis possible. The meiotic chromosome, in its less active phases is not much better. For pure developmental biology (as opposed to evolution ary biology) meiotic recombination is almost irrelevant, except as part of the mechanism needed to use genetics as an experimental tool. With out any doubt the most important form of the chromosome is the active form found in interphase. Unfortunately this is the least rewarding form to study microscopically. But even here, in the extremely favour able case of the giant polytene chromosomes (especially of Drosophila , with its excellent genetics) cytological studies have, from the point of view of the molecular biologist, been somewhat disappointing. Puffs are certainly revealing and their detailed study increasingly rewarding but the meaning of bands and interbands, the exact location, nature and control of the genes for most ordinary enzymes (such as those, say, for the Krebs cycle), or the genes for fundamental developmental processes (such as the homoeotic mutants) are not only unknown but are unlikely to be discovered by cytological methods unassisted by molecular biology
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