260 



CARL C. LINDEGREN 



EXTRACHROMOSOMAL INHERITANCE 



When a pure haplophase culture of red yeast (adenine dependent) is 

 planted on an agar plate, both red and white colonies appear. When the white 

 colonies are subcultured, only white colonies appear. The red cells when 

 planted on a second plate continue to produce both red and white colonies. 

 The white colonies are stable variants derived from red. Bacterial variations 

 of this type are ordinarily called gene mutations, but bacteriologists have 

 been unable to test their so-called mutations by breeding experiments except 



While Normal 

 (Adenine Independent) 



Red Original Culture 

 (Adenine Dependent) 



White Normal 

 (Adenine Independent) 



Red Subculture 

 (Adenine Dependent) 



White Variant 

 (Adenine Dependent) 



Red Subculture White Variant White Subculture 



Normal X (Adenine Dependent) (Adenine Dependent) (Adenine Dependent) X Normal 



Hybrid 



(White Culture, Adenine Independent) 



ASCI Analyzed 

 White (Adenine Independent) 

 White (Adenine Independent) 

 Red (Adenine Dependent) 

 Red (Adenine Dependent) 



Hybrid 



(White Culture, Adenine Independent) 



ASCI Analyzed 

 White (Adenine Independent) 

 White (Adenine Independent) 

 Red (Adenine Dependent) 

 Red (Adenine Dependent) 



Fig. 16.2 — Inheritance of pink versus white colony in Saccharomyces. The white mutants 

 derived from pink produce pink offspring and are indistinguishable from the original pink 



genetically. 



in a few cases. The white cultures have lost their color but they are still 

 characteristically adenine dependent like their red progenitor. Breeding ex- 

 periments (Fig. 16.2) have been carried out with the white yeast cultures 

 derived from the red. When the derived white cultures were used as parents, 

 they produced precisely the same kind of offspring as the original red culture 

 from which they arose. This proves that the change from red to white did 

 not affect a gene. The change from red to white may, therefore, be called a 

 differentiation since it occurs without gene change. 



The phenomenon of Dauermodifikation which was first described by JoUos 

 (1934) has thus been confirmed in yeast genetics. The stable change from 



