CHROMOSOMES AND GENES 



65 



tacks upon the problem existing — Moewus' 

 claim of a single sex-gene in the Flagellate 

 Chlamydomonas and Hofmeyr's data on 

 crossing over between a sex-determiner and 

 other loci in Papaya.) But very recently 

 two important facts have come to light. The 

 first is that all loci of the X-chromosome in 

 Drosophila have now been covered by dupli- 

 cations in triploid intersexes (Bedichek) 

 without finding a sex-shifting locus. The 

 other is Knapp's proof for the liverwort 

 Sphaerocarpus that some X-chromosome 

 segments of very different length, produced 

 by radiation, shift the sex in the clear-cut 

 alternative, which means that the smallest 

 of the fragments contains all the properties 

 for the decision of the sexual alternative 

 which are located in the X-chromosome. 

 The latter fact shows conclusively that in 

 this case no other sex-genes are littered over 

 the sex-chromosome, whereas Bedichek 's 

 case proves only the absence of a single sex- 

 determining locus, without giving informa- 

 tion about an eventual multitude of them. 

 (The latter point has been discussed earlier 

 by Goldschmidt.) These facts then raise 

 the question in connection with our present 

 discussion, whether or not both sides to the 

 old discussion are wrong. Could it not be 

 that there are no sex-genes, one or many, 

 but only an action of the whole chromosome, 

 or in other cases of a segment thereof, in 

 the form of what we discussed as a pattern- 

 effect? I realize that this question appears 

 absurd or even ridiculous to the orthodox 

 geneticist, who believes that the X-chromo- 

 some is a long string of genes, some of which 

 affect eye-color and wing-structure, etc., 

 others in between being concerned with sex- 

 determination. Therefore, an action of the 

 whole cannot be distinguished from an 

 added action of the individual genes, ac- 

 cording to their conception. But once the 

 idea of the corpuscular gene is discarded, 

 our question ceases to be absurd and even 

 assumes a very important meaning. The 

 future will bring the answer. 



Thus we have reached the point at which 

 we may draw conclusions from the selection 

 of material upon our problem which has 

 been presented. The most general conclu- 



sion is that the entire recent development of 

 genetics leads away from the classic theory 

 of the particulate gene which reproduces 

 itself and plays its own independent 

 (though cooperative) role in controlling the 

 processes of development. I know that 

 there are many geneticists who realize this, 

 but prefer to try first a broadening of the 

 conception of the gene which would make 

 it possible to pour new wine into the old 

 bottles (Muller, Stadler). I think this is 

 patch-work which cannot last and that the 

 body of facts already available justifies a 

 radical change in our conception of the 

 genetic structure of the chromosome. This 

 does not mean that everything is already 

 perfectly clear, or that I do not realize the 

 amount of work which has to be done to 

 clear up every point. But I think that 

 such work is more likely to lead to success 

 if its direction is clearly recognized and if 

 it is not chained to an outgrown theory. I 

 think that the crudeness of the explanation 

 of position-effect in terms of genes and the 

 * ' genes for mutation ' ' are a sufficient warn- 

 ing. The direction which is indicated by 

 the facts which were reported (and whole 

 groups of facts have not been mentioned 

 because offering indirect evidence only) is, 

 in my opinion, the following : Apart from 

 the chemical interactions between the thy- 

 monucleic acid and the proteinic heredi- 

 tary material, which is not yet understood, 

 the chromosome is in many respects a unit 

 in a chemical sense and acts as such. There 

 may even be concerted actions of more than 

 one chromosome. This action of the chro- 

 mosome as a whole is bound (to what extent 

 we do not know) to the normal serial pat- 

 tern of the chromosome, just as the chemical 

 properties of a chain molecule are deter- 

 mined by its serial pattern of radicals. A 

 disturbance of the serial pattern changes 

 the normal action into another one. But 

 there is in addition a more or less localized 

 action of smaller or larger sections or blocks 

 of the chromosome. Any change of serial 

 pattern within these sections produces again 

 a definite abnormality of development, with 

 a possible variability of the effect, accord- 

 ing to the type of the new pattern. We do 



