ENZYMK- FORMATION OF DEOXYRIBONUCLEIC ACID 



105 



that the labelled deoxyribonucleotide was subsequently used for DNA 

 synthesis. In the experiment described in Fig. 2 DNA was synthesized 



Fig. I. Time curve of DX.A formation from tritium or ''-P-labelled CMP, as 

 measured by the incorporation of isotope into DNA [7, 8]. Incubation conditions 

 for one time point: o • i ^tmole of labelled CMP, i o /^^mole of ATP, 5 -o /^imoles of 

 MgCl,, o-i mg. of heated DNA (10 min. at 100 ) and 4-5 mg. of "enz\Tne", 

 final volume 0-41 ml., pH 7 -4, 37^. 



CMP ►DNA 



t ^ t ' ^ 



Micrococcal DNA-se | Pancreatic DNA-se 



+ spleen diesterase ,+ venom diesterase 



\-® 



Md 



Fig. 2. Enzymic degradation [9] of DNA formed from P*--CMP. 60 min. 

 incubation with conditions as in Fig. i. 



from ^'-P-CMP and, after isolation, degraded enzymically in two different 

 ways : 



(o) With pancreatic DNA-se + snake venom diesterase. These enzymes 

 split DNA as indicated by the arrow in Fig. 2 and produce 5'-deoxy- 

 ribonucleotides. Since 5 '-labelled CMP was the precursor in the synthesis 



