Ovogenesis

OVOGENESIS is a set of processes occurring in the gamete of the embryo sac of flowering plants and constituting the very process of formation of the egg, which develops as a result of the complete division of second-order oocytes. That is, oogenesis is the transformation of haploid germinal material (haploid - the genotype of a given organism contains only half of the homeolog genes, therefore, contains half of the hereditary information of its “double”, called a homologue) into the diploid gamete of female germ cells. The biological basis of sexual reproduction is the recombination of genes from paternal and maternal cells and their association within the haploid of male eggs and, conversely, the diploid of male germ cells (spermatids). Oogenesis begins after fertilization, when the egg grows and swells in the uterine stigma. The developmental stage of the female germinal oocyte is accompanied by two successive mitotic divisions through meiosis and produces a diploid mother cell, or egg. Genetic information is inherited from two heirs, the sperm (boy) and the egg (girl). This process can result in an XY or XX karyotype in males and females, respectively. Spermatids undergo meiosis on their migration route through the ovary, where they reach maturity in the female egg (oocyte).

In mammals and birds, oogenesis begins in embryos developing from intermediate epiboly cells called hypoblasts, which multiply rapidly to form so-called sister chromatic cell structures. Two meiotic divisions, each resulting in haploidy, determine the genetic code of the daughter nuclear cells and lead to meiosis, which is responsible for the formation of male or female sexually mature gonads. And the completion of the process of oogenesis leads to the formation of aneuploid (diploid, like the parental zygotes), gynandritic ovaries containing both sexes. In females, such ovaries exist in pairs, called paramesonephric gonads, which have a different location and size in each animal species, depending on the nature of reproduction (dioecious animal species or hermaphrodites). In turn, one female paramesorephrotic gonad carries a small functional ovary at one of its poles, known as the fallopian tube. The opposite part, directly connected to the uterus, has a generative tubular ovule or hemicaryon, although its origin has also been hypothesized to be of uncertain origin. In its thickness there are one or