CHAPTER IV 

 THE SUPREMACY OF GENES 



t. The Type of Nucleic Acids and Its Biological 

 Significance 



In cells there are two kinds of nucleic acids, one of which is 

 desoxyribonucleic acid (DNA) and the other ribonucleic acid (RNA). 

 DNA is usually present in nuclei, and the nucleic acid in genes is 

 believed to be DNA, whereas RNA is found as a rule in cytoplasm, 

 mostly being contained in particles known as microsomes which there- 

 fore can be regarded as elementary bodies or their aggregates contai- 

 ning RNA in rich amount. In addition, particles called mitochondria 

 are said also to contain this nucleic acid, but the particle present are 

 much fewer in number than microsomes which the latter are reported 

 to occupy even 15 to 20 per cent of the cytoplasm. 



These particles must have directing influences upon the whole 

 cytoplasm when genes are separated from the latter, since they 

 contain nucleic acid in rich amount and form large sized particles. 

 Most likely they, if liberated from the cell, may first and foremost 

 behave as viruses, no matter whether the cell has the normal struc- 

 ture or the structure changed by a virus ; in the latter case particles 

 will be regarded as the virus having multiplied in the cytoplasm. 



The nucleic acid in phage particles separated by ultracentrifuga- 

 tion are reported to be mostly DNA, while their lipid content is poor. 

 On the other hand, chromosomes which may be regarded as aggre- 

 gates of genes similarly contain DNA but no lipid, a fact which may 

 enable one to consider the bacterial particles isolated as phage to be 

 bacterial genes. Cytoplasmic particles such as microsomes and mito 

 chondria contain nucleic acid in rich amount as mentioned above, but 

 in contrast to genes the nucleic acid is RNA and in addition, 30 to 40 

 per cent of the particles are composed of lipids (27) (28). 



Such large lipid contents of these cytoplasm particles may partially 

 account for their submission, in spite of their high nucleic acid 

 contents, to the genes. The difference in the kind of nucleic acids^ 

 however, may have on this point a much more important significance. 



According to the writer's concept, when inserted among protein 



