Duplication with 

 labeled thymidine 



1st c-metaphase 

 after labeling 



Duplication without 

 labeled thymidine 



2nd c-metaphase 

 after labeling 



Fig. 2B. For legend see page 74. 



Fig. 2C. Diagrammatic representation of the distribution of subunits of DNA 

 during chromosome duphcation. Although the subunits are not resolved by micro- 

 scopic examination, they are represented and distributed as indicated by the 

 observed pattern of labeling in Figs. 2A and B. Broken lines represent labeled 

 subunits and unbroken lines represent unlabeled subunits. The dots represent 

 grains in the autoradiograms. (From Taylor et al., 1957.) 



75 



