Chromosomes and Genes 165 



cists would accept this today, though the idea crops up again from 

 time to time. 



2. A gene produces primary products at its locus in the chromo- 

 some, which react with those of other loci. The first reaction will be 

 with the neighboring products; if these are changed by the rearrange- 

 ment which brings different genes into the neighborhood, a different 

 reaction is produced. More specific is the modification of these 

 theories used by Stern, partly in explanation of the dosage effects 

 (Last, 1948; see below). He assumes that the gene has two inde- 

 pendent attributes: combining power for a substrate, and the effi- 

 ciency with which the substrate is converted into gene product. The 

 position effect then is the disadvantage of the gene in the new position 

 in regard to access to the substrate with consequent decrease in 

 gene product. In the Dubinin effect, the advantage of the allele in 

 the normal chromosome comes also into play. 



Even if we assume that genie action takes place in this way 

 (we shall return to this point in the next chapter, when discussing 

 Pontecorvo's and Lewis' ideas), we do not understand why the effect 

 is never anything but the typical mutant effect of the assumed gene 

 and not at times something quite different, though in Stern's formu- 

 lation a plus-minus effect is assumed. I cannot help feeling that this 

 is nothing but a pseudochemical circumscription of the phrase "po- 

 sition of the gene," and we shall see later in the chapter on dosage 

 that Stem himself has moved away from these notions. 



3. Our own interpretation is presented in this chapter and is 

 based upon replacing the gene by a chromosomal pattern. 



4. A completely different theory has been proposed by Ephrussi 

 and Sutton (1944). After showing that a theory involving chemical 

 interactions at the surface of the chromosome does not work, they 

 conclude that one must look for a structural hypothesis. This means 

 that some change in the physical state of the chromosome must be 

 involved. Muller (1935i>) had already discussed such a possibility 

 pointing to the forces of attraction between different chromosomes. 

 If a similar force should act between different loci, a kind of stress 

 could be produced by abnormal neighborhoods which would result 

 in distortions and therefore change of chemical action of the gene. 

 (We might think of such "distortions" as mentioned in the quotation 

 frqm Mothes, I S C c ee hhh.) Following these ideas of Muller, 

 Ephrussi and Sutton argue: Recent work on the myosine molecule 

 has shown that a fibrous protein exercises an enzymatic property 



