Genie and Non-genic Parts of the Chromosome 21 



coils to which large amounts of DNA are attached in quantities and 

 configurations typical for the individual chromomere. Since these ac- 

 cumulations of DNA ( fig. 1 ) may be controlled by a gradient centered 

 in the centromere, the typical differences of these chromomeres are 

 not a function of their individual chemical or physical constitution but 

 a function of their position in the chromosome. Is the naked chro- 

 monema non-genic and the chromonema coil (if existing) plus nucleic 

 acid or the nucleic acid alone genie? The facts reported on structure 

 hardly permit us to draw a conclusion. Actually, they show that the 

 whole question is wrongly put, a question which is derived from the 

 a priori idea of the gene string. Later discussions will revert to this 

 point and suggest a solution of the difiBculties. At the present stage of 

 our discussion it might suflBce to point out that it is, in my opinion, 

 impossible to assert that definite parts of the chromonema play the 

 role of the string in a string of beads, while the beads themselves are 

 alone the important factors, that is, the genie material or individual 

 genes. However, it remains a fact that whatever complication of 

 morphological shucture is found in the chromosomes has to do with 

 the chromomeres. Therefore, in our search for the genie material, we 

 must scrutinize more carefully these structural elements. 



The term "chromomeres" was first applied to the structure of 

 leptotene and pachytene chromosomes, which were assumed to be 

 fully stretched chromosomes. However, when speaking of chromo- 

 meres in a comparative way, we must always specify which chro- 

 momeres are meant. Actually, chromomeres are found at different 

 levels of spiralization of the chromosome and are therefore not strictly 

 comparable. At one end of the series are the large chromomeres seen 

 in diakinesis of large chromosomes and found to be constant in a 

 given chromosome. Their number is small, say in the neighborhood 

 of ten. These are clearly not the same chromomeres that are typical in 

 the leptotene and pachytene stages of animals and plants. These are 

 again individually constant and synapse point by point, thus showing 

 their specificity. Their number is about a hundred. Therefore the 

 diakinetic chromomeres are compounds of the pachytene ones in the 

 order of magnitude of ten per package. This must be the result of 

 denser spiralization, which, however, is so exactly alike in the two 

 homologues that the chromomere-by-chromomere synapsis still holds. 

 The salivary gland chromosomes (with transitions in chromosomes of 

 other dipteran tissues ) are on a different level. There is no doubt that 

 the bands or discs of these chromosomes are chromomeres (more 



