Phenogenetics

Phenogenetics, the doctrine of the realization of hereditary traits. The development of any trait in an animal is a complex process, depending both on the external environment and on many genes present already in the fertilized egg, and later in the cells of the body. The resolution of the question of how genes influence the development of traits, how the realization of the genotype in the phenotype occurs, is the task of a special direction in genetics, named by V. Haecker (Naeske) phenogenetics. Haecker gave the following program for phenogenetic analysis: 1) establishing the specific nature of the trait (its morphology, histology, physiology); 2) studying the process of development of the property; 3) establishing the moment in the development of the trait from which a difference in it begins to appear in two races (phenocritical phase); 4) tracing the causes of these differences back to the germ cells. In this way, according to Haecker's thinking, the actual connection between genes and traits could be established. Haecker himself gave a number of examples of phenogenetic analysis and showed that the phenocritical phase for different traits is at very different stages of development - from very early to very late. - Phenogenetics as a complete science does not yet exist, but already there are many works that approach the problem of hereditary realization from different sides and bring genetics closer to mechanics (or physiology) of development. The main task of phenogenetics is conceived as the study of the essence of gene action in development. This is approached by various indirect routes: by studying the phenotypic effect of individual genes (especially lethal ones), by clarifying the effect of external conditions on the phenotypic effect of genes, by studying a series of allelomorphs of the same gene, combinations of genes, the most complex interaction of which occurs in the development of traits, the phenomenon of pleiotropy (see). More and more facts are accumulating showing how certain genes depend on the finest aspects of organismal development, often very early stages of development (up to the stage of two to four blastomeres), complex intracellular processes (separation of chromosomes, etc.). A number of genes affects growth, i.e., in other words, the rate and direction of cell divisions. Apparently, genes 'act' in individual cells, coming into some, as yet unknown, interaction with the cell protoplasm. The effect of a number of genes is manifested in changes in the rates of certain reactions in the organism. By studying the effect of temperature on the effect of a gene, it was possible to show that the gene affects the formative reaction at a specific period of time, different for different genes. At the same time, depending on the temperature, the effect of the gene also changes accordingly (see Heredity, modern foundations of the doctrine of heredity). These facts speak in favor of the viewpoint that genes produce chemical substances - enzymes, catalysts, the role of which is to change the rates of certain formative processes. The idea of the gene itself as a catalyst was first given by Driesch, and later developed by Hagedoorn (the gene as an autocatalyst). R. Goldschmidt gave these views the most general form, creating the so-called physiological theory of heredity. He arrived at it on the basis of his work on sex determination in the silkworm. From Goldschmidt's point of view, the gene, constantly present in the cell, begins to exert its specific influence on the development of a particular phenotype when the amount of a specific enzyme - of that gene - reaches a certain minimum value. Goldschmidt's ideas, despite the fact that they are not without flaws in a number of points and are not shared by many geneticists, are very valuable and will play their role in the further development of the little-researched question of the action of genes in development.

P. Rokitsky S : (C_eH₄OH)_a Phenolphthalein,

C,H₄<Q>0 CO (Ph. VII). White powder (with a faint yellowish tint), with m.p. +253°. Almost insoluble in water, soluble in alcohol, somewhat less soluble in ether. Soluble in alkaline water; with alkalis it is colored bright red, for which reason it serves as an indicator in titration. Transition of color at pH 8.3-10.0. Phenolphthalein is obtained by condensation of phthalic anhydride with phenol; it is the progenitor of an extensive series of preparations (nosophen, tetragon, eosin, fluorescein, iodeosin), obtained by condensation of phthalic anhydride with resorcinol and other phenols; some phenolphthalein preparations are used for recognizing liver diseases. In doses of 0.05-0.5 it has a laxative effect; it is included in a huge number of patented laxative preparations. The most famous is purgen. Phenolphthalein, passing through the stomach without decomposing, in the intestine is converted into a readily soluble but poorly diffusing sodium salt, causing irritation of the rectum, which is the reason for the laxative effect. It is excreted in the urine and colors it red if there is ammonia in the urine, formed during the breakdown of urea. The use of phenolphthalein is sometimes accompanied by side effects: weakness of the heart, hemolytic phenomena, and irritation of the kidneys.