TRANSDUCTION BY STAPHYLOCOCCAL BACTERIOPHAGE

13 We wish to thank Dr. R. L. Sinsheimer of the California Institute of Technology for his interest and suggestions along this line. 14 Ingram, V. M., Nature, 180, 326 (1957); Hunt, J. A., and V. M. Ingram, Nature, 181, 1062 (1958). 15 It should be made clear that here "mutation" does not include gross or direct effects of mutagenic agents on DNA or chromosomes to produce deletions, inversions or other abnormalities which render a particular gene inactive or modify its phenotype effect. It seems reasonable for purposes of study of the induction process to divide "mutations" into at least two classes: (1) those mutations probably involving one DNA nucleotide pair and exerted through the process of gene replication and (2) those mutations involving one or more nucleotide pairs exerted finally through some physical or chemical action on DNA (or RNA) and not through gene replication. In the case of UV-induced mutation it appears that the former by far exceed in number the latter (if they occur at all). Further this is not to suggest that one nucleotide pair may somehow "code" a particular amino acid but rather that a change in the nucleotide composition of the nucleotide pair unit in a particular sequence may lead to a change of one amino acid originally specified by the particular sequence involved to another amino acid.