THE DEOXYRIBONUCLEIC ACID CONTENT OF THE NUCLEUS 



163 



TABLE V 



Average Amounts of DNA per Nucleus in Tissues of Young and Adult Mice. 



AS Obtained by Photometric Determinations on Feulgen Preparations'^ 



Swift^^ made an extensive study of ten different tissues in the mouse. The 

 results, reported in Table V, demonstrate the presence of polyploidy in 

 some organs and the constancy of the DNA content of the diploid nuclei 

 (class I), this common value of DNA being twice that found in spermatids. 

 This is in good agreement with the figures from chemical analysis reported 

 above. This relationship of DNA to the number of chromosomes is evident 

 also during the formation of gametes. During spermatogenesis, primary 

 spermatocytes contain four times the amount of DNA found in the sper- 

 matids, as is consistent with the fact that one primary spermatocyte will give 

 four spermatids after the two meiotic divisions. This fact has been demon- 

 strated by Lison and Pasteels in Talpa,^^ by Schrader and Leuchtenberger 

 in Arvelius albopunctatus^^ and by Swift in the mouse. ^^ An identical pro- 

 cess was described by Alf erf^ in oogenesis in the mouse ; he found that pro- 

 nuclei resulting from two meiotic divisions carry one-fourth of the DNA 

 that is contained in primary oocytes. 



The results originally obtained by Pasteels and Lison^« on different organs 

 of the rat seem to be in disagreement with those of the American workers; 

 the DNA content of the nuclei of some organs (liver, pancreas, adipose 



" L. Lison and J. Pasteels, Compt. rend. soc. biol. 143, 1607 (1949). 

 *' M. Alfert, J. Cellular Comp. Physiol. 36, 381 (1950). 



