O 4 



20 40 60 80 100 120 140 160 180 200 



FRACTION NUMBER 

 Fig. 6. 



Puromycin inhibition of hlstone biosynthesis in the absence of DNA replication. (Fig. 3, 

 Chalkley and Maurer, Proc. Natl. Acad. Sci. U.S. 54, 498, 1965; reproduced with per- 

 mission of the National Academy of Sciences.) 



- HISTONES FROM CALF ENDOMETRIUM CHROMATIN 

 S (nuclei incubotion) 



*ni*ix 



FRACTION NUMBER 



Fig. 7. 



Biosynthesis of hlstones in incubated. Isolated nuclei. (Fig. 1, Chalkley and Maurer, 

 Proc. Nail. Acad. Sci. U.S. 54, 498, 1965; reproduced with permission of the National 

 Academy of Sciences.) 



136 



