Analyses of spontaneous and induced mutations of the tobacco mosaic virus

Various types of analyses of the existing data on spontaneous and X-ray induced mutations of the tobacco mosaic virus to the aucuba variant are discussed on the basis of the known phytopathological, biochemical and biophysical facts. It is concluded that if virus protein is the X-ray absorbing medium through which the mutation is induced 3% of the total virus protein would be involved in this primary process. If nucleic acid were the medium through which the ionizing energy must be absorbed in order to induce the mutation, 25% of the amount of this acid existing in the virus would be needed. The analysis shows also the complete insignificance of the naturally occurring ionizing radiations for the process of spontaneous mutation of the virus.