PROBLEMS OF MEASUREMENT OF MUTATION RATES 



21 



first, then the anti-B, and then the Ulex, and, a second time, using the 

 anti-A first and then the anti-B and the Ulex. This first curve repre- 

 sents the proportion of the activity remaining in cells versus the num- 

 ber of stages with anti-A and A carrier. This is an AB individual to 

 start with. We see that he has 7 x 10"^ non-A cells. 



Now, we continue the same experiment and remove a very large 

 proportion of the remaining cells with anti-B and B carrier, and finally 

 a further removal with Ulex and carrier. Then, the reverse experi- 

 ment is done. With the anti-B first, he has 10"^ non-B cells. Most of 

 these are A. When both of the reagents are used in tandem, of course, 

 you have to come out at the same level whichever the order of removal. 

 It does make that much sense, at least. 



When we use Ulex to remove the cells that are ostensibly at the 

 end of this experiment, we remove some, and the difference between 



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STAGE 



Figure 4. Isotope dilution curves showing phenotypic subpopulations 

 in two AiB bloods. The criterion of cell phenotype is coagglutination 

 with the agglutinin and its corresponding carrier cells. Phaseolus anti-A, 

 human anti-B and Ulex anti-H are used in sequence: solid points= 

 anti-A first; open points=anti-B first. 



