Early embryonic development is controlled by the genome of both maternal and embryonic . Oocyte maturation , fertilization and the first cleavage divisions characterized by a lack of effective transcription , hence these processes are completely controlled by the factors of maternal origin . Persistence of maternal transcripts depends on the length of the poly (A ), which may be lengthening or shortening . Starting embryonic genome is species-specific and occurs after several cleavage divisions . It connects with the gradual disappearance of maternal mRNA. It has been demonstrated significant differences between the expression profile of genes in embryos produced in vivo and in vitro , which is associated with the imperfection of culture conditions in vitro. Growth hormone ( growth hormone , GH) , produced in the anterior pituitary, stimulates the growth of the organism after birth. Functions of GH in the regulation of mammalian embryo development remain controversial. So far it has been shown that the gene is expressed in GH preimplantation mouse embryos , bovine and rat and bovine oocytes . In addition, GH receptor mRNA was located in the ovary , uterus and placenta and bovine embryos, bovine and mouse. Were also present in the embryo transcripts (mRNA ) for growth factors such as IGF -I, IGF- II. Known positive effect of exogenous GH the potential for development of bovine and mouse oocytes in vitro . Pituitary transcription factor (PIT - I) is the primary regulator of GH gene transcription process . Recent reports indicate that the presence of the gene transcript in oocytes , zygotes and embryos bovine 8BL to the stage . These results may demonstrate that GH exerts para-and autocrine at this stage of ontogenetic development .