TABLE I 



Base Compositions of Sea Urchin RNA Fractions 



Fractions I-IV from Arbacia embryos exposed to PO4 from fertilization to early blas- 

 tula. 28S and 18S RNA from.) raiacia eggs labeled with ^ PO4 during oogenesis. Hydrolysis, 

 separation of nucleotides and determination of base composition according to Salzman, 

 Shatkin and Sebring (1964), except for compositions of bulk (total) RNA and DNA (sperm), 

 which are from the literature. Approximate centers of gravity in sedimentation profile 

 corresponding to fracUons I-IV: 28S, IBS, lOS, 3S. 



^ Table I, Gross, Kraemer and Malkin, Biochem. Biophys. Res. Comm. 18, 569, 1965; repro- 

 duced with permission of Academic Press. 



«S«B:>f»73- . Avr~'.-.f^- ' 



0.25 



0.20-- 



» 0.I5-- 



0.10 



0.05- - 



40 60 



% FRACTION 



Fig. 3. 



(Fig. 1, Gross, Kraemer and Malkin, Biochem. Biophys. 

 Res. Comm. 18, 569, 1964; reproduced with permission of 

 Academic Press.) 



Fig. 2. 



