CONTENTS 



Chapter Page 



The Effect of the Environment on Adapta- 

 tion to a Deficient Medium 22-1 



Slow Adaptation to the Absence of Panto- 

 thenate by a Pantothenateless 

 Mendelian Recessive 22-4 



Adaptation to the Absence of Pantothenate 

 by a Regularly Segregating, Slowly 

 Adapting Culture 22-9 



Demonstrations of the Genie Nature of the 



Adaptation 22-12 



Synthesis of Pantothenate by Gene B . . . . 22-16 



Alternate Route of Synthesis 22-16 



Mutation in the Presence of Pantothenate . . 22-18 



Growth of the Recessive Culture in the 



Absence of Pantothenate 22-22 



Mutation in the Absence of Pantothenate . . 22-24 



Randomness of Mutation in the Absence of 



Pantothenate 22-27 



Competition Between Adapted and Unadapted 

 Cells in Limiting Concentrations of 

 Pantothenate 22-31 



The Functions of Recessive and Dominant 



Alleles in Adaptation 22-36 



Conclusions 22-38 



23 The Balanced Lethal - Saccharomycodes .... 23-1 



The Accumulation of Lethal Genes 23-5 



Reversion of n to N 23-6 



24 Chromosome Maps 24-1 



Tetrad Analysis and Centromere Linkage . . 24-1 



25 Proof of Interchromosomal Transfer of Heredi- 

 tary Material by Tetrad Analysis 25-1 



Conversion of Recessives to Dominants in 



the Heterozygote 25-1 



26 Irregular Segregations as Supporting Evidence 



for Gene Conversion 26-1 



The Origin of Nonfermenters of Maltose . . 26-9 

 Genetical Analysis of Transformed ME 



Alleles 26-9 



Tests for Cytoplasmic Effects by Dr. 



Doudoroff and our Staff 26-13 



Conclusions from Dr. Doudoroff s Experi- 

 ments 26-25 



XVI 



