LIFE CYCLES 



1-9 



ber of variants which may appear, while in the haplophase most 

 variants become apparent and are easily discovered. 



d. When the diploid cells spomlate to produce haploid cells, 

 tetrad analysis of the 4 spores has proved that a reduction division 

 occurs. Hybrids heterozygous for as many as 12 alleles have been 

 analyzed, all of which segregated regularly in the ascus. 



Haplophase generally 

 transitory but repro- 

 duction by budding may 

 continue for variable 

 lengths of time. Haplophose may 

 become completely stabilized 



Ascus 2-$pored 

 Spores non-viable 



■^O 



Jygosoccharomyces 



Fig. 1 -7 Legitimate and Illegitimate Diploids. 



Extensive pedigrees of many generations are available for nu- 

 merous characters, and four linkage groups have been demonstrated. 



These facts prove conclusively that the terms haplophase and 

 diplophase can be used as definitely in speaking of yeasts as of or- 

 ganisms in which the cytological evidence is more complete. It is 

 necessary to transfer diploid cultures frequently if they are capable 

 of producing spores in order to maintain the original characteris- 

 tics of the cultures. If sporulation occurs, new genotypes are seg- 

 regated and variability appears. In this connection it is interesting 

 to observe that industrial yeasts are usually grown in broth, and 

 transfers are made by pipetting a large proportion of the sediment 

 from the original culture into the transfer. This technique mini- 

 mizes the possibility of variation. 



