ON THE SIZE OF GENETIC DETERMINANTS IN PNEUMOCOCCUS AND THE NATURE OF THE VARIABLES INVOLVED IN TRANSFORMATION

Abstract

Simultaneous absorption and transformation measurements have been carried out with quadruply marked deoxyribonucleic acid (DNA) degraded by mechanical shear. A large part, although not necessarily all, of the observed loss in transforming activity can be attributed to decreased absorption of DNA. The size of genetic markers is small, possibly of the order of several nucleotides. There are probably 2 types of absorption site on the pneumococcal surface, one of which absorbs only DNA of molecular weight greater than about 2.2x106. A constant number of moles rather than a constant weight of DNA, is probably bound by each type of site at saturation. The molar binding constant for DNA by bacterial sites is constant in the range studied below Mn = 2.2x106. For each marker the probability of incorporation into the bacterial genome has a characteristic dependence on molecular weight.