80 



THE THEORY OF THE GENE 



abnormal) (see chart, Fig. 19) ; but in other notches the 

 lost region extends over fewer units. In each case the test 

 seems to mean that a small piece (more or less) of the 

 chromosome has, in some sense, dropped out. 



white 

 facet—— 



b 



aDnor-m. 



/ 



\-not ver 



ver .... v ev 



1-14 Mel 



/-not v/el 



a 



Fig. 46. 

 Diagram a, showing the location of the genes in the Notch-bearing 

 chromosome. In the right-hand rod the break in the chromosome 

 stands for Notch. In the left-hand rod the location of three reces- 

 sive genes (white, facet, abnormal), that stand opposite Notch, are 

 indicated. In b the translocation of a piece of an X-chromosome to 

 another X is shown. There are two vermilion-bearing X-chromo- 

 somes to one of which the piece is attached carrying the normal 

 allelomorph of vermilion, i.e., not-vermilion. In c there are two 

 yellow-bearing X-chromosomes to one of which is attached a piece 

 carrying the normal allelomorph of yellow, i.e., not-yellow. 



As has been stated, recessive genes, when opposite to 

 notch, produce their recessive characters. This is con- 

 sistent either with the view that these recessives are 

 absences and the effect is produced by all the rest of the 

 genes, or with the view that the recessive genes are pres- 

 ent and produce their effect in combination with all the 

 rest of the genes. The result does not permit a decision 

 between the two views. 



