Genie and Non-genic Parts of the Chromosome 47 



cc. Conclusions from bacterial transformation 

 and transduction 



The most potent claim for the genie nature of DNA is derived 

 from the amazing phenomenon of bacterial transformation (GriflBth, 

 1928; Avery, MacLeod, and McCarty, 1944; and many others since), 

 to which recently the phenomenon of transduction has been added 

 by Lederberg (see Lederberg, 1952; Lederberg and Tatum, 1953; 

 Zinder and Lederberg, 1952; Zinder, 1953). Unencapsulated pneumo- 

 cocci could be made to transform into an encapsulated type as an 

 inherited change under the influence of a substance derived from a 

 capsulated strain, which turned out to be DNA. Boivin et al. ( 1945 ) 

 found similar results for Escherischia coli, but not with the same 

 regularity. Alexander and Leidy (1953) found the same in a very 

 different bacterium, Hemophilus influenzae, another parasitic bac- 

 terium, where the transforming agent comes from streptomycin- 

 resistant strains. Since the first discovery, it has been shown in 

 pneumococcus that several different kinds of transformation can be 

 performed, each through the action of a particular nucleic acid from a 

 particular mutant strain. 



One character involved is the capsule (a shell of polysaccharides 

 secreted around the bacterium), which may appear rough or smooth. 

 It is known that one is derived from the other by mutation, but 

 transformation can produce either type according to the origin of 

 the transforming agent. Intermediate types are produced by quanti- 

 tative mutation, depending on the amount of the secreted polysac- 

 charides. The nucleic acid extracts of these intermediate types trans- 

 form rough strains into exactly the same phenotype of intermediaries. 

 The intermediate mutants are thus based upon a mutation ( = produc- 

 tion of an allele) of the normal capsular agent. No mutation of one 

 intermediate type into another has been found and no two such 

 specific types simultaneously. (The geneticist drawing parallels with 

 higher forms might say — assuming bacteria to be haploid — that this 

 is a set of multiple alleles which have been produced directly from 

 the original rough form.) 



Another cell character has been described as extreme rough 

 (Taylor, 1950; see also Ephrussi-Taylor, 1951), arisen by mutation 

 from rough. This can be transformed to rough by nucleic acid ex- 

 tracts from both rough and smooth strains. In reverse the extracts 

 from extreme rough can transform rough into extreme rough. Thus, by 



