Genie and Non-genic Parts of the Chromosome 33 



telophase and early prophase this quantity doubles, as it would be 

 expected to do if the synthesis for the following division takes place 

 at this stage and not during mitosis. This is also confirmed by the 

 fact that radioactive phosphorus is taken into the nucleus on a 

 large scale only at this time. For other material it is maintained that 

 the doubling of DNA by synthesis occurs at another time. Since the 

 visible doubling of the chromosomes seems to occur at different 

 stages in different cells, sometimes as early as telophase, such varia- 



•=10 



E 



sperm 

 C 



/ 



/v 



/ 



endosptrm 



12 C 24C 





2.5 



5 10 



DNA- Feulgen 



20 



40 



Fig. 2. Relative amounts of DNA in nuclei of maize kernel and mature pol- 

 len. A 2:4:8:16 series is evident in the scutellum, and a 3:6:12:24 series in the 

 triploid endosperm. (From Swift, 1953; reproduced by permission of the author 

 and the Academic Press, Inc. ) 



tion appears quite possible. In meiosis, synthesis of DNA for all 

 four division products occurs before leptotene, with subsequent dis- 

 tribution to first and second cytes and spermatids (ova) in a ratio of 

 4:2:1, a fact which closely parallels the visible behavior of the tet- 

 rads. 



The authors who did most of this work seem to be unanimous 

 in their assumptions ( Swift, 1953 ) : "DNA is the one constituent of 

 chromosomes showing the quantitative behavior that might be ex- 

 pected from a carrier of genetic specificity . . . RNA [as opposed 

 to DNA] apparently shows some variability between malignant and 



