Genie and Non-genic Parts of the Chromosome 25 



B. CONCLUSIONS FROM BIOCHEMISTRY 



a. Chemistry of the chromosome 



At this point we turn to biochemistry for more information. It is 

 rather disconcerting that in the chromosomes, which should have a 

 very comphcated and diversified chemical structure, only a few 

 components have thus far been isolated that are the same in chro- 

 mosomes of the most diversified forms of animals and plants. This is 

 in contrast to our knowledge of other active stuffs, which, though 

 differing in different groups, seem to be within the groups always 

 derivatives of a single chemical type: many hormones are sterols; 

 many vitamins are amino acids; all the dubitable sex stuffs of Kuhn 

 and Moewus were said to be derived from crocin; all enzymes are 

 probably proteins. But the few types of proteins which have been 

 found in chromosomes do not give us much information. The claim 

 that different parts of the chromosome contain varying fractions of 

 these proteins does not seem to be generally accepted. Thus the state- 

 ment that the chromosomes contain chain molecules of proteins does 

 not convey much genetical insight and does not set apart the chro- 

 mosomes from other cell structures. 



A different situation exists with the nucleic acids. Though only 

 the two, DNA and RNA, have been isolated, we have at least one 

 important fact: DNA is a typical constituent of the chromosomes 

 which is hardly found outside the chromosomes, though it occurs 

 sometimes in mitochondria and sometimes in the cytoplasm. RNA, 

 however, is predominantly at home in the nucleolus, the nucleus out- 

 side the chromosomes, and in the cytoplasm. Thus DNA has estab- 

 lished a predominant claim either to be the genetic material or to be 

 necessary for the function of the genetic material, while RNA cannot 

 be genetic material sensu strictu. This does not mean that RNA is 

 unrelated to the function of the chromosome and, eventually, to its 

 genie functions in some indirect way. RNA might be used in synthesis 

 of DNA, or DNA might be the source of formation of RNA; neither 

 theory thus far can be checked. But one thing is certain: DNA is con- 

 stant in the chromosomes, while RNA is produced and again removed. 

 The most convincing case (apart from the behavior of the nucleolus 

 and the removal of RNA through the nuclear membrane) is that of the 

 so-called elimination chromatin in Lepidoptera. Seiler (1914) found 

 that in the lepidopteran egg during meiosis a considerable amount of 

 "chromatin" is sloughed off all chromosomes and remains visible for a 



