Evolution.

Society for Experimental Biology

Date:: 1953

Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Evolution. Source: Wellcome Collection.

475/484 (page 443)

POSTSCRIPT 443 may easily be modified by a variety of experimental agents in such a manner that they produce new high polymers. A further problem, still on the chemical level, is that of the chemical evolution of genes themselves. We know that in groups of related animals compounds of the same functions are produced, e.g. haemoglobins, phosphatases. These compounds, though of the same function, display differences in chemical composition. To what extent are the analogous genes, which control the production of these compounds of identical function, themselves identical? Is it possible that the chemical evolution of genes themselves is a controlling process in evolution? If genes of identical function but from different organisms were chemically identical, there would appear to be no reason why these genes would not be able to function in foreign organisms. For example, if a gene responsible for haemoglobin synthesis in cows is chemically identical with a similar gene in rabbits, the rabbit gene should be able to function in a cow, etc. We know that genes can function fairly efficiently when transferred by crossing between closely related species, but we do not know whether chemical changes occur in the genes themselves when reproducing in foreign species. Nor do we know whether a gene can function and reproduce in a relatively unrelated species. Some viruses appear to change their antigens, to some extent, in different species. Thus Rous sarcoma virus, when isolated from chickens, ducks or pheasants, has chicken, duck or pheasant antigens, but also retains a characteristic Rous virus antigen in all three cases. Perhaps genes behave in the same way. It is important, for our understanding of mechanisms of evolution, to acquire information on these points, for if the genes of one species can only function in a few closely related species, evolution is limited by the gene evolution possible within species or species groups. But if individual genes can flourish in a wide variety of foreign species, then it is perfectly possible that genes will be transferred, by a variety of accidential processes, between relatively unrelated species. Whilst such events will seldom be of importance in ordinary breeding ex¬ periments, they might be of great importance in the time scale of evolution. No one would wish to deny the probable importance of the evolution of the intrinsic genetic equipment of a single species, but it is probably true to say that inadequate attention has been paid to the possible influence on evolution of recruitment of genetical material from without a species, by other than mating processes. The transfer of viruses between relatively unrelated species is not uncommon. The evidence for transmission of transforming factors between bacteria, without mating, is indisputable. We do not know to what extent viruses and transforming factors may be incorporated in chromosomes and so added to the Mendelian system of