CHROMOSOME AND GENE STRUCTURE 7 



nucleus. This is indicated diagramatically on fig. 2. We 

 may be quite sure that this localisation of chemical sub- 

 stances has special chemical and physical significance. 

 One thing which is very clear is that often this locali- 

 sation keeps substrates apart from the enzymes which 

 would otherwise destroy them or utilise them prior to 

 the onset of the physiological activity for which this 

 process is useful. For example the co-existence of phos- 

 phate esters and of phosphatases which are active at 

 cellular p^ is only made possible by this physical sepa- 

 ration of the substances concerned. As soon as the bio- 

 chemist, by grinding or other maceration procedures, 

 breaks down this organisation on the chemical level, 

 phosphate esters are rapidly destroyed, and with them 

 the characteristic cycles which are involved in glucose 

 metabolism. 



Chromosome and Gene Structure 



The structures about which most details are available 

 are the chromosomes. There are two very different main 

 theories of the structure of the chromosome. One is 

 that it consists of at least one polypeptide chain running 

 the full length of the chromosome, with discrete bodies, 

 known as chromomeres, distributed along it. The chro- 

 momere, according to this theory, consists of material 

 additional to that contained in the long polypeptide 

 chains. Each chromomere has at least one gene and may 



