THE GENETICS OF TUMOR TRANSPLANTATION 



>87 



The most important and critical scries of crosses were tliose in which 

 tumor 13714BX, originating in an Fi generation mouse, was used for 

 transplantation. 



This tumor, inoculated in F2 generation mice gave 94+:25o— . This 

 indicated that either 4 or 5 genes were involved. The experimental results 

 lie between the expectation for this number of genes and afford no basis for 

 choice as to the exact number. 



Fig. 130. — Diagram showing the relationship existing between the various stocks 

 and generations of mice employed by Bittner in studies of transplantable tumors 

 arising in hybrid mice. The two parent strains are called "A" (albino) and "D" 

 (dba or dilute brown). Two arrows pointing towards a square indicate that the 

 particular generation was produced by crossing the two stocks or generations from 

 which the arrows come. One arrow indicates that the matings were inter se to produce 

 the next generation. {From Bittner.) 



The most interesting figures come, however, from the two backcross 

 generations, that of Fi X A (ZBC) and that of Fi X D (iBC). The actual 

 figures, compared with expectation for various numbers of genes which are 

 introduced by the respective parent stocks, are shown in Table 8. 



It appears, therefore, that probably four or five pairs of genes, of which 

 one or two are introduced by the A stock and three or four are introduced by 

 the D stock, are involved. 



The fact that the evidence provided by the backcross generations sup- 

 ports the probability that four or five genes are involved, is important. 



