Ontogenesis, Developmental Genetics

Ontogenesis is the process of individual development of an organism from the moment of its birth to death. It includes embryonic or embryonic development, which occurs from the moment the egg is fertilized until the young individual emerges from the egg membranes or the mother's body, as well as the postembryonic period, which begins after birth.

Human embryogenesis can be divided into several periods, each of which is characterized by certain features. In medical practice, two concepts are usually used: the embryonic period, which lasts the first 8 weeks of the body’s development, and the fetal period, which begins from the 9th week, that is, from the moment the rudiments of organs are formed.

The study of heredity and variability has shown that the sequential development of the characteristics of an organism in ontogenesis occurs under the control of the genetic apparatus. At different stages of ontogenesis, coordinated regulation of the activity of various genes occurs. The mechanisms of this regulation and the specific sequence of deployment of the genetic program in the ontogenesis of various species of organisms are being intensively studied.

Although all cells in an organism potentially carry the same genetic program, as the organism develops, different cells use different parts of that program. The nature of gene work is greatly influenced by environmental conditions in relation to the cell and the given organism. Detailed information about how gene activity is regulated has so far been obtained in microorganisms, and this process in higher organisms, including humans, remains to be studied.

However, it is already clear that the regulation of gene activity in higher organisms occurs continuously throughout ontogenesis. A lot of data has been accumulated on how certain genes are “turned on” at different stages of development of a given organism and in its different organs.

For example, during the course of a person’s life, the type of hemoglobin molecules synthesized changes three times. In the early stages of embryonic development, so-called embryonic hemoglobin is formed. Then, after some time, the gene that controls the synthesis of these molecules “falls silent” (suppressed), and another gene encoding the so-called fetal hemoglobin comes into operation instead. Later, another change occurs, the synthesis of the third type of hemoglobin begins - adult type hemoglobin. The need to replace one type of hemoglobin with another is due to the different needs of the body.

Also, the study of developmental genetics has shown that at different stages of ontogenesis, the formation of various organs and systems of the body occurs, as well as their interaction. For example, the formation of the nervous system begins in the early stages of embryonic development, and it is a process that occurs throughout ontogeny.

In addition, developmental genetics studies not only the normal development of the body, but also disturbances in this process, which can lead to various congenital pathologies and diseases.

In general, the study of ontogenesis and developmental genetics plays an important role in understanding the mechanisms of the formation of the body and its functioning, and can also help in the development of new methods for diagnosing and treating various diseases.