302 



Hubert P. Yockey 



recessive lethal gene mutations play an important role in the lethality of diploid 

 cells. Since it is possible to present a calculation of the equivocation due to 

 this process let us calculate the survivorship curve according to this notion and 

 see how it compares with experiment. 



100 



50000 

 X-RAY DOSE.ROENTGENS 



75000 



100000 



Fig. 1 . Percent survival for yeast with one irradiated parent. Haploid x haploid 

 cross (oo), haploid x diploid cross (oO), etc. The first symbol represents a cell 

 of the a-mating type, the second one of ^-mating type. A filled letter o designates 

 the irradiated parent. Haploid dominant lethal curve: Q, 9o; %,o% ; 6, •©; 

 9,0*. Diploid dominant lethal curve: n^ •O' ■>0*; D, •©; Ho*. 

 Diploid survival curve: A' • — aa diploid, ^, 9 — aa diploid. Haploid survival 

 curve: A> • — a haploid; ^,9 — a haploid. (From ref. (61)). 



The decay of the correct read-off probability is given by equation (10) of 

 my paper in Part I : 



^^P.(j) = -J(^)Pi(j) + im (6) 



In the diploid case J(X) cannot contain a constant tenn because of the protection 

 afforded by the unaffected allelomorph. Therefore dp/ij)ldX must depend at 

 least linearly on ?^. The polynomial for J{X) is in this case, where J^ is a 

 constant: 



m = /i^ (7) 



Substitute this function in equation (4) 

 dJ 



1 JX = P^^"^ ^^ 





J,?. 



(8) 



