THE HEREDITARY ORDER: GENETIC INFORMATION 



crystal. Schrodinger adds that we believe the whole chromosomal 

 fiber to be an aperiodic solid. 



Chromosomes have been known to cytologists for a long time. 

 They are relatively large and easy to stain, and they stain heavily — 

 hence their name, which means "colored bodies." 



As early as 1866, Haeckel realized that the nucleus, which contains 

 the chromosomes, is the cellular organelle which is responsible for 

 the maintenance and transmission of the inheritable characters. And 

 Weismann, in 1892, understood that the inheritable characters were 

 located in the chromosome. The chromosome, according to 

 Weismann, is composed of spherical bodies, or ides. Each ide con- 

 tains determinants, and each determinant is composed of biophores, 

 which all represent a different character. The biophore corresponds 

 to the actual gene, that is, to the unit of genetic material, the unit 

 of biological order. 



The quantitative study of the transmission of hereditary characters 

 had been started in 1865 by Gregor Mendel. But Mendel's laws 

 remained ignored until, in 1900, they were rediscovered inde- 

 pendently by Hugo de Vries, Correns, and Tschermak. This was 

 the beginning of formal genetics. Each gene was assigned a specific 

 place on the chromosome. But it was not until 1944 that the genetic 

 material was identified chemically, and not until 1953 that its 

 structure was disclosed. 



The living being — the organism, the unit of life — has been 

 defined as an independent system of integrated structures and func- 

 tions. It is a highly complex system, able to reproduce its kind, that 

 is, to multiply the specific biological order. What is the molecular 

 basis of biological order and specificity? How is order stored in the 

 organism? If a molecule is unable to divide, how is a molecule of 

 hereditary material reproduced? 



Necessity of Variation 



The statement that the organism reproduces its kind is of course 

 true, but only statistically true. If the primitive living being had 

 always given birth to an identical system, life would probably have 

 disappeared long ago as the result of the drastic changes undergone 



[15] 



