28 MUTATIONS 



determined by additional criteria. We have a specific anti-Ai, the 

 extract of DoHchos beans, and so, in an individual that is Ai, it was 

 possible to find out how many of the cells are phenotypically A2, as 

 well as how many are phenotypically 0. 



Incidentally, it was possible to find out, in an AiB, what proportion 

 of cells were A2B, as well as just B, and this was done with the idea 

 of telling whether somatic crossing over or other processes that give 

 horaozygosis is the main origin of exceptional cells. The answer was 

 that AoB cells were present. They are not homozygotes. Homozygosis 

 is therefore not the only thing involved; we must also have some 

 change from Ai to Ao. 



Some have argued that Ao may be a quantitative change in the ag- 

 glutinogen rather than a real difference in specificity. I prefer the no- 

 tion that it has difTerent specificity. 



In any case, in these two polycythemics we followed both the non-Ai 

 and the total non-A cells. We did the regular isotope dilution experi- 

 ments with both Dolichos anti-Ai and lima bean anti-A. 



The first one did this (Fig. 7). This is time (abscissa), and each one 

 of these points is the level that we obtained with an isotope dilution 

 experiment, this array of ]ioints being the non-Ai with Dolichos (Fig. 

 8, A.R.), and this (Fig. 7, A.R.) being simply non-A. 



Notice that with lima bean anti-A, after the initial changes you are 

 left with a stable increase 170 days later. There is another point, not 

 on this figure, which is about a year later. It is only a little below 

 this last point. This, then, is some sort of stable change. You can ask, 

 how does this change compare with stability of the levels in normal 

 individuals? We have only a few data on this. I would say that it is 

 much more stable in the normal individuals than in those who had 

 the P^-. You have only a little variation over periods of three years, 

 and that variation is technical error, I am convinced. This is not 

 technical error. 



Now, what happened here (Fig. 7) ? This may be partly technical 

 error, because we found the specificity of the Dolichos is influenced a 

 great deal by the temperature at which the experiments are done. 

 This is not true of the lima bean. Therefore, with summer coming on 

 here, we may have an artifact in this curve. 



Auerbach: Excuse me, but what does this original rise signify? 



Atwood: What does it suggest? Figure 8 is another case, and we see 

 just a rise of the total non-A (Fig. 7, G.P.). On the other hand, we 

 see this early spiking of the assumed non-Ai (Fig. 8, G.P.) . I wouldn't 

 think too much about the reliability of this kind of spiking, unless it 



