The article discusses the genetic control of biochemical reactions in Neurospora, focusing on how genes regulate specific chemical processes. It highlights the importance of physiological factors in population mechanics, which operate independently of genetic changes. Examples include homing reactions in salmon and birds, conditioned mating preferences in birds, and reactions in ants toward colony mates. The study emphasizes the role of genes in controlling biochemical reactions, with a focus on the genetic control of development and metabolism. The research uses Neurospora as a model organism, as it offers advantages for genetic studies. The study involves x-ray-induced mutations to identify genes responsible for specific biochemical reactions. For example, mutant strains of Neurospora were found to be unable to synthesize certain vitamins, such as B6 and B1, and para-aminobenzoic acid. These mutants were studied to determine their inheritance patterns and to understand the genetic basis of their metabolic deficiencies. The research also describes a method for measuring growth by observing the linear progression of mycelia along a horizontal tube. The findings suggest that the inability to synthesize certain vitamins is controlled by a single gene. The study concludes that this approach provides a promising method for understanding how genes regulate development and function. The research also highlights the potential for discovering new essential substances, such as vitamins and amino acids, through the study of mutant strains. The study demonstrates that the genetic control of biochemical reactions is a critical aspect of physiological genetics.The article discusses the genetic control of biochemical reactions in Neurospora, focusing on how genes regulate specific chemical processes. It highlights the importance of physiological factors in population mechanics, which operate independently of genetic changes. Examples include homing reactions in salmon and birds, conditioned mating preferences in birds, and reactions in ants toward colony mates. The study emphasizes the role of genes in controlling biochemical reactions, with a focus on the genetic control of development and metabolism. The research uses Neurospora as a model organism, as it offers advantages for genetic studies. The study involves x-ray-induced mutations to identify genes responsible for specific biochemical reactions. For example, mutant strains of Neurospora were found to be unable to synthesize certain vitamins, such as B6 and B1, and para-aminobenzoic acid. These mutants were studied to determine their inheritance patterns and to understand the genetic basis of their metabolic deficiencies. The research also describes a method for measuring growth by observing the linear progression of mycelia along a horizontal tube. The findings suggest that the inability to synthesize certain vitamins is controlled by a single gene. The study concludes that this approach provides a promising method for understanding how genes regulate development and function. The research also highlights the potential for discovering new essential substances, such as vitamins and amino acids, through the study of mutant strains. The study demonstrates that the genetic control of biochemical reactions is a critical aspect of physiological genetics.