Some Introductory Ideas Concerning the Application of Information Theory in Biology 55 



individual. Gowen (15) also prepared six strains of mice by sibling malings 

 for twenty or more generations. When survival was tested the survival ratios 

 were 1, 14, 34, 63, 64, 83 and 88 per cent. These results again stress the 

 importance of individuality as Gowen pointed out.* 



Point Mutations and Chromosome Aberrations 



We have now arrived, via our discussion, at territory familiar to the radiation 

 biologist. This is the controversy over the role played by point mutations and 

 chromosomal aberrations induced by deleterious agents such as x-rays. This 

 subject has been ably discussed recently by Muller, Kaufmann, Giles, Carlson, 

 SwANSON and Stadler, and by Kimball (16). The point of view of these 

 authors varies. Kimball takes the stand with Lea (17) that the death of cells is 

 due to chromosome aberrations which become effective at cell division. Swanson 

 and Stadler point out that the two effects occur together and that a clear cut 

 separation has not yet been accomplished. Muller points out some difficulties 

 with the mutation by breakage interpretation. Russell (18) states that gross 

 chromosomal aberrations, although they cause early death of embryos, are 

 probably not an important radiation hazard to man. 



From the point of view of this article each of these effects is a way of intro- 

 ducing disorganization in the genome. The point mutation mechanism is the 

 biological analogue of the 'white noise' of the communications engineer. The 

 other extreme is not found in communication engineering but involves a strong 

 correlation between errors and is reflected as a loss of whole paragraphs or 

 other gross mutilation of the message. Each of these extreme cases will be 

 important in applications of information theory in biology. Unfortunately, the 

 second case has not been studied mathematically and so it is not known how 

 to calculate the equivocation it introduces. 



It is therefore necessary to proceed with the calculation of only the part of 

 the equivocation which corresponds to point mutations. Since one of our 

 objectives is to develop a fundamental theoretical treatment of radiation hazard 

 to man, Russell's comment encourages one to think that this procedure is 

 v/orthwhile. It should be remembered that equivocation from these two extreme 

 conditions may have the same dependence on the deleterious influence. This is a 

 point which requires further mathematical study. 



The Interaction of the Deleterious Agent nith DMA and the Decay of H 



According to the Watson and Crick model of DNA there seems to be no 

 biochemical reason why there should be an interaction between nucleotide 

 pairs. The biological requirements for protein specificity do not seem to demand 

 an intersymbol influence (19). The matter is not closed, but the evidence favors 

 regarding the interaction of a deleterious agent with a nucleotide pair to be of 

 the first order. 



We have previously suggested that the action of ionizing radiation or other 

 deleterious agent may be such that the nucleotide pair is altered in such a way 

 that it mimes another symbol as far as protein synthesis is concerned (6). It 



* Individuality as an integral feature in biology has been emphasized recently by Rcxier J. 

 Williams: in Biochemical IncUvidiiality, J. Wiley and Sons, New York, Chapman & Hall, 

 London (1956). 



