EARLY EMBRYOGENESIS AND SECONDARY SEX RATIO IN TRANSPLANTATION OF PREIMPLANTATION EMBRYOS IN VIVO

Abstract

In the natural process of embryogenesis, one, less than two eggs are produced, unlike in the biotechnology of embryo transfer, which allows hormonal treatment to produce dozens of eggs at once. This leads to a discrepancy, sometimes to a large extent, between the formation of male and female gametes at gametogenesis (primary sex ratio) and the sex of progeny at birth (secondary sex ratio). In fertilization, male zygotes form more than female zygotes due to the higher fertilization activity of male spermatozoids compared to female sperm. In the mother’s body, as a result of neuro-humoral and biochemical regulation by means of a «development block», embryos with genetic disorders are discarded. Male embryos, as the primary carriers of abnormal genes, are more susceptible to this process. The disparity between primary and secondary sex ratios is related to differences in the living conditions of the mother, as these conditions determine the number and significance of genetic disorders in embryos that are degenerated during embryogenesis. Embryos in incomplete degeneration, after extraction from the donor’s uterus, are restored and continue to grow and develop in a cultured environment. In partially damaged embryos, the ability to totipotent development is restored after the transfer of a surrogate mother whose own «development unit» does not recognize foreign embryos.