Since the Russian edition of this book was published in 1975 many new research works have appeared which have made necessary some additions for the English edition, to reflect progress in molecular developmental genetics. Recent important findings in this field have brought about essential corrections to the concept of genetic regulation of the process of cell differentiation. The discovery of the mosaic structure of a gene prompted the re evaluation of our considerations about the regulation of gene activity in eukaryotes, and the data about transcriptional events during ontogenesis are of great importance as well. Formerly it was generally accepted that a derepression of genes was responsible for cell differentiation in the process of develop ment. Recently three important conclusions have been derived (Davidson and Britten, 1979) which help to pose the problem in a new way: 1) Only a small part of single copy sequences of DNA is represented in nuclear RNA of a given type of cell or tissue: 10% to 20% in sea urchin embryos, 11 % in rat liver, 4% to 6% in Drosophila cell culture, etc. Since only about 10% of single copy sequences represent the structural genes (Davidson and Britten, 1973), transcription of almost the whole set of structural genes occurs.Purified enzymes, extracted from both types of homozygotes (LV-a/LV-a and LV-b /LV/b), are identical in a number of ... Therefore, the enzyme activity in tissues is regulated by a number of enzyme molecules (Schimke, 1973). Oganji ... It is also known that mutations which change the degradation rate of catalase in mouse liver do not affect its degradation in the kidneys (Ganschow and Schimke, 1970).
|Title||:||Gene Interactions in Development|
|Author||:||L. I. Korochkin|
|Publisher||:||Springer Science & Business Media - 2012-12-06|