312 PHYSIOLOGICAL GENETICS 



2. The proportional relation between the quantitative effect 

 of X rays ami the amount of ionization is parallel for mutations 

 and rearrangements. 



3. Temperal lire shocks that increase the rate of mutal ions also 

 produce chromatin rearrangements, in both animals and plants. 



4. Mutations induced by X rays and spontaneous mutations 

 are identical. 



5. The phenotypic effect of rearrangements, i.e., the so-called 

 position effect, under which must be included all the effects that 

 have been described as mutations occurring simultaneously with 

 rearrangements, is of the same type as the effect of so-called 

 gene mutations. We find all the known types of genie effect. 

 In fact, many effects that originally were regarded as due to gene 

 mutation have turned out to be position effects of rearrangements. 

 Specifically, the following types may be mentioned, using the term 

 position effect now for all phenotypic consequences of whatever 

 rearrangements. 



a. Dominant and recessive effects. 



b. Effects of the type of a dominigene effect (cubitus inter- 

 ruptus) . 



c. Different position effects produced by different rearrange- 

 ments involving the same locus behave like a series of multiple 

 alleles (scute, notch, Bar). 



d. "Invisibles" — mutations or rearrangements without visible 

 effect. 



e. Effects of the modifier type; e.g., the so-called mutant 

 Beaded produces alone only a nick in the wing of a percentage 

 of individuals. If combined with an inversion, this effect is 

 modified into the real beaded type. The inversion may be 

 replaced by others in the same region with the same effect, and 

 the removal of the inversion also removes the modifying effect 

 (Goldschmidt, unpublished). 



/. Cases in which the effect of the mutant gene is proportional 

 to its dosage. There are chromosome rearrangements exhibiting 

 the same phenomenon, e.g., the Bar case. 



g. There is a most remarkable parallel between the spontaneous 

 appearance of so-called gene mutations and effects of rearrange- 

 ments. Goldschmidt (in press) analyzed a series of cases of 

 complicated rearrangements occurring spontaneously within 

 different lines of Drosophila, which led to the appearance of a 



