A substance isolated from heat-killed, virulent pneumococci which when added to cultures of living, non-virulent bacteria cause virulent pneumococci to appear. Thus bacteria of one phenotype are transformed to an alternative phenotype by a non-living material. The demonstration that the PTP is DNA rather than protein was one of the earliest lines of evidence that genes are made of DNA. See Chronology, 1928, Griffith; 1944, Avery, MacLeod, and McCarty; transformation.
Subjects: Genetics and Genomics.