CYTOGENETIC ANALYSIS 495 



Fig. 69. Peripheral-blood derivatives of man. 



Xi? 



r 



1 ^ 



x 



f<: 



t> *%z^ 





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Mitotically active leucocytes prepared by the technique of Nowell 948 and stained with 

 lactic-acetic-orcein by (Mrs.) R. Lang in the laboratory of Dr. P. Gerald, The Children's 

 Hospital Medical Center, Boston. (Photographs by R. Kato.) 



Top. The author has interpreted one of the two X chromosomes from this peripheral 

 derivative of a normal female as being the submetacentric pair exhibiting lack of chromatid 

 separation, due probably to the retarded development of extensive segments of hetero- 

 chromatin. Other cells from this individual have unequivocally displayed the counterpart 

 of the A : A 2 condition noted in the Chinese hamster. The existence of a sex-determining 

 (somatic) principle other than the assumed XX: XY scheme in man requires application of 

 the differential tritiated-thymidine-uptake pattern noted for sex elements by Taylor 1316 and 

 confirmed by Yerganian and Grodzins (unpublished data). 



Bottom. The author has interpreted the "retarded" element as the X x chromosome in 

 man. Note the fuzziness and delayed separation of chromatids which characterize sex 

 elements during metaphase. 2400 X. 



