340 



SPECULATIONS ON CELLULAR ACTIONS 



we consider that a gene might be inactivated by a change in a relatively 

 small chemical group in the gene "molecule," it seems reasonable that 

 m might be quite small, perhaps unity. 



Some of the foregoing notions can be visualized qualitatively by ref- 

 erence to Fig. 3. Two ionization tracks are shown crossing a single cell. 



Fig. 3. Qualitative relations between a cell, two ionization tracks, and some relevant 

 entities involved in the model of Fig. 1. See text. 



The lower one has just been formed. Ions and excited fnolecules are 

 present. The H2O"'' ions, which are assumed relevant to the specific 

 action described in Fig. 1, are designated by circles and are all located 

 directly in the path of the fast ionizing particle. All other entities pro- 

 duced by the ionizing particle (all excited molecules and all ions except 

 H2O''") are irrelevant and are designated by crosses. One possible path 

 by which relevant entities may diffuse to the precursor is shown. Note 

 that the H20'^ starts to diffuse and reacts to form an OH radical (one- 

 pronged circle). The radical diffuses a bit and reacts to form a molecule 

 of H2O2 (two-pronged circle) which finally, by diffusion, chances to col- 

 lide and react with the precursor (decisive process) . The upper track is 

 older than the lower. All the relevant and irrelevant entities are sepa- 



