Chapter 14 

 VARIATION IN GROWTH AND FERMENTATIVE CAPACITY 



THE "D" FAMILY 



Lindegren and Lindegren (1944) developed a large family of 

 haploid and diploid cultures originating from a single diploid cell 

 of S. cerevisiae. Cultures originating from (a) vegetative cells, 

 (b) single ascospores dissected from 4-spored asci, (c) intact 4- 

 spored asci, and (d) 1-spored asci were critically examined in an 

 analysis of four inbred generations of the "D" family (p. 14-2). 

 The individual cultures in the pedigree are designated as follows: 

 Arabic numerals indicate asci; capital letters designate the asco- 

 spores isolated from asci. For example, DIA is the culture from 

 ascospore A isolated from ascus Dl. Four spores were dissected 

 from each 4-spored ascus; in ascus Dl only two spores (DIA and 

 DIB) produced viable colonies. DlC and DID died and are not lis- 

 ted in the pedigree. Only one spore, D2B, from ascus D2 produced 

 a viable colony. Single ascospore cultures may be either haploid 

 or illegitimately diploid or mixed, but data concerning the genetic 

 composition of the single ascospore cultures in this pedigree are 

 not available. 



Small Roman letters designate subcultures arising from indi- 

 vidual colonies obtained by sowing a suspension of cells on an agar 

 plate. For example, the original D culture was plated on agar and 

 fourteen colonies, Da - Dn, selected, The yeast was grown in 8 x 1 

 inch tubes in 20 cc. of broth containing 1.6 per cent sucrose and 1.4 

 per cent corn steep water solids. After 48 hours the contents were 

 shaken up and 10 cc. poured into a Hopkins vaccine tube and centri- 

 fuged. The volume of yeast was read off directly in hundredths of 

 a cc. per 10 cc. of medium. All fourteen subcultures yielded more 

 than 6.0 hundredths of a cc. 



The original D culture was placed on gypsum, and two 4-spored 

 and three 1-spored asci were isolated. The two 4-spored asci were 

 dissected and the spores planted separately in culture tubes. Only 

 three of the ascospores from the 4-spored asci produced cultures, 

 while all three 1-spored asci germinated and each produced a visi- 

 ble culture. The yield, that is, the crop of cells collected by cen- 

 trifuging 10 cc. of the broth, of the cultures originating from the 1- 

 spored asci approximated that of the single colonies selected by 

 plating diploid vegetative cells. This indicates that 1-spored asci 

 are genetically similar to the vegetative cells from which they arise. 



14-1 



