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Currently, rapidly developing computer and digital technologies are widely included in variousspheres of life. Their rapid development and widespread using have stimulated the development and improvement of artificial intelligence systems that allow solving various complex tasks, applying them in variousfields, including scientific,technological, medical and others. The article discussesthe terminology and principles of artificialintelligence systems, aswell asmodern opportunities and prospects for the use of technologies created on their basis, the directions of their application in reproductive medicine to solve various scientific problems and practical tasks. It can be used in the diagnosis and assessment of the risk of development of various diseases and complications, genetic testing and evaluation ofitsresults, prediction of pregnancy and fertility assessment, analysis of germ cells, also asselection ofthe highest quality embryosin in vitro fertilization programs and in solving othertasks.

The review presents generalized current data on sperm aneuploidy in healthy (fertile) men and infertile male patients with a normal karyotype and with chromosomal abnormalities. The mechanisms of aneuploidy in germ cells, factors affecting of its level, the relationship with defects of spermatogenesis, meiosis, decreased sperm parameters, as well as the effect of sperm aneuploidy on male fertility, embryo development and gestation are discussed.

Modern titanium dioxide nanomaterials, in particular modified with nanosilver, have antiviral, antibacterial, antifungal activity, cytotoxic effects in vitro experiments and can affect germ cells of warm-blooded laboratory animals. The research aims to study the effect of different types of titanium dioxide nanoparticles on the physiological and biochemical characteristics of wild boargerm cells in vitro. When applying the maximum dose (LD50) of the studied nanopowders in all samples, sperm survival was probably lower than in the control: by 41.9% (р<0.001) ‒ under the action of TiO2 nanoparticles (hereinafter NPs) (Frantsevich Institute for Problems of Materials Science of NAS of Ukraine, hereinafter IPM), by 28.0% (р<0.05) ‒ under the action of TiO2 NPs (Acros Organics), by 53.5% (р<0.001) ‒ under the action of 4% Ag-TiO2 NPs (IPM) and by 55.9% (р<0.001) ‒ are the action of NPs 8% Ag-TiO2 (IPM). Nanopowders of different based on titanium dioxide manufacturers, characterized by similar morphological characteristics and varying degrees of nanosilver addition (Ag content from 0 to 8%), starting from a dose of 1/10 LD50, can have a damaging effect on the germ cells of wild boars, which is manifested by a decrease in the respiratory activity of sperm and cytochrome oxidase activity, by increasing succinate dehydrogenase activity. The most sensitive marker was the sperm survival rate, the value of which significantly decreased under the action of 8% Ag-TiO2 nanoparticles (IPM) at a dose of 1/100 LD50, which is a consequence of disruption of the activity of mitochondrial enzymes and, accordingly, resynthesis of ATP. Our results confirm and extend the data on the nature of the damaging effect of titanium dioxide-based nanoparticles on germ cells of warm-blooded animals due to oxidative stress. The obtained experimental data will be taken into account in the hygienic regulation of the investigated nanopowders. [ABSTRACT FROM AUTHOR]

Introduction. The risk of infection with SARS-CoV-2 virus and potential cross-infection in an in vitro fertilization laboratory remains unclear. SARS-CoV-2 enters the body through angiotensin-converting enzyme 2 receptor. There is a possibility that high expression of angiotensin-converting enzyme 2 on testicular cells can lead to spermatogenesis disfunction and decreased quality of the ejaculate.The study objective is to compare quantitative and qualitative sperm characteristics in patients who sought medical help at the Laboratory of Genetics of Reproductive Disorders at the Research Centre for Medical Genetics with reproduction problems between 2017 and 2020 with a focus on the period of COVID-19 pandemic.Materials and methods. Results of semen analysis of 4403 patients (mean age 34 years) were considered. Taking into account histories of patients examined in 2020, a separate group of 428 men was formed with 42 men with a history of coronavirus infection confirmed by lab tests (40 cases of mild disease, 2 cases of moderate disease). In 14 patients, sperm analysis was performed twice: prior to COVID-19 and after. Standard sperm analysis was performed in accordance with the World Health Organization Guidelines. For statistical analysis Student’s t-test was used with significance level p

Drosophila protein GAGA (GAF) is a factor of epigenetic transcription regulation of a large group of genes with a wide variety of cellular functions. GAF is encoded by the Trithorax-like (Trl) gene, which is important for the formation of various organs and tissues at all stages of ontogenesis. In our previous works, we showed that this protein is necessary for the development of the reproductive system, both in males and females of Drosophila. Decreased expression of the Trl gene led to multiple disorders of spermatogenesis and oogenesis. One of the significant disorders was associated with massive degradation and loss of cells in the germline. In this work, we carried out a more detailed cytological study to determine what type of germ cell death is characteristic of Trl mutants, and whether there are disturbances or changes in this process compared to the norm. The results obtained showed that the lack of GAF protein causes massive germ cell death in both females and males of Drosophila, but this death manifests itself in different ways, depending on the sex. In Trl females, this process does not differ phenotypically from the norm. In the dying egg chambers, signs of apoptosis and autophagy were revealed, as well as morphological features that are characteristic of the wild type. In males, Trl mutations induce mass germ cell death through autophagy, which is not typical of Drosophila spermatogenesis, and has not been previously described, neither in the norm nor in other genes’ mutations. Thus, GAF lack in Trl mutants leads to increased germ cell death through apoptosis and autophagy. Ectopic cell death and germ line atrophy are probably associated with impaired expression of the GAGA factor target genes, among which there are genes that regulate both apoptosis and autophagy.

This review addresses the concept of ontogenetic origin of health and disease (DOHaD) and the new concept of paternal origin of health and disease (POHaD). These concepts are based on scientific evidence that environmental factors impacting mother or father can play a role in reprogramming the health of their off springs throughout their life span. Moreover, the changes that have arisen can be transmitted through generations via diverse epigenetic mechanisms. Terms, such as epigenetics (a kind of “driver” for these concepts), epigenetic inheritance (including Intergenerational Inheritance – from generation to the next generation and Transgenerational Inheritance – through generations), epigenetic changes caused by the environment (Environmental Epigenetics) are discussed. Vulnerable periods towards epigenetic changes (Windows of Susceptibility) that occur in male germ cells responsible for epigenetic inheritance are considered. Epigenetic epidemiological studies in the field of reproductology are described; their advantages and disadvantages are discussed. These studies can serve as the basis for obtaining new knowledge about the causes of epigenetic variations in germ cells that occur in health and upon exposure to environmental factors as well as the inherited phenotypic outcomes.

The paper covers the legal and ethical aspects of sex selection, and the dynamics of public opinion on this issue in different countries and regions of the world. Also, the results of two questionnaires, organized by Research Centre for Medical Genetics (2000 and 2017), are analyzed.

The study objective is to evaluate spermatogenesis using the method of quantitative karyological analysis of immature germ cells from the ejaculate sediment (QKAIGC) in patients with azoospermia or cryptozoospermia with normal and low semen volume.Materials and methods. Seventy-two (72) semen samples from patients with suspected azoospermia were analyzed, 48 with normal semen volume (≥1,5 ml) and 24 with low semen volume (

Male factor contributes significantly to the problem of infertile marriages. Alterations of morphological and/or functional characteristics of germ cells can result in infertility. We analyzed 122 semen samples – 55 samples with normal (≥ 15 million/ml) sperm concentration (group I) and 67 samples with cryptozoospermia or severe oligozoospermia (concentration < 1 million/ml, group II). Standard semen analysis and quantitative karyological analysis of immature germ cells from ejaculate (QKA IGC) (patent L.F. Kurilo № 2328736, 2007) were performed for all samples. The results of QKA IGC are significantly different in the two groups analyzed. The proportion of IGC at stages of preleptotene-zygotene and pachytene is verified to be higher (p < 0.01) in the sperm samples with normal concentration (group 1), indicating spermatogenesis arrest at prophase I of meiosis. In the semen samples of group 2 (patients with cryptozoospermia or with severe oligozoospermia, sperm concentration < 1 million/ml) proportion of spermatocytes II and spermatids is significantly higher than in the group with normal sperm concentration, that indicates the spermatogenesis arrest at the stage of sperm formation (spermiogenesis). IGC index in 58 % of the samples from the group I is higher than normal IGC index. For the majority of the samples from the group II the IGC index was not estimated because of lack of spermatozoa. In all sperm samples with suspected azoospermia examined through QKA IGC spermatozoa were identified (44 samples from group II). Thus, if azoospermia is suspected, QKA IGC can be recommended to patients as an alternative to diagnostic testicular or epididimal biopsy. QKA IGC is unique in the assessment of the of spermatogenesis dynamics, as it is precise, safe, non-invasive and time-saving method that allows multiple repeated evaluation of IGC at different stages of spermatogenesis.

Method of quantitative evaluation of the immature germ cells, their pathology in mitosis and meiosis (in semen, embryo and fetal ovaries, of gonad biopsies or fragments of sectioned material) is informative method and should be introduced into the clinical practice in andrology and gynecology and fundamental research. Quantitative analysis of mitosis and female meiosis development was initiated on experimental animals and fetal gonads from spontaneous or therapeutic abortions.

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Polyzoospermia is extremely high (above 250 mln/ml) sperm concentration with normal volume of ejaculate. In the laboratory of genetic disorders of reproduction of Research Centre for Medical Genetics in 2007–2012 years we analyzed more than 14 000 semen samples from infertile men and men with reproductive disorders in order to study the distribution and characteristics of spermatogenesis in polyzoospermic men. Only polyzoospermic men semen analysis results were interpretered in present article. Polyzoospermia (sperm count over 250 mln/ml in volume over 1,5 ml) was detected in 191 semen samples (1.3 %). At the same time 15 % of the samples with polyzoospermia were normozoospermic. Among 85 % of the sperm pathology samples asthenozoospermia occured most frequently (77 %), astenoteratozoospermia was detected in 8 % of cases with polyzoospermia. The average proportion of vitality was 90.09 ± 10.02 %, normal morphology – 14.93 ± 8.51 %, and progressive motility – 17.72 ± 11.81 %. The average concentration of spermatozoa in the ejaculate in the examined samples was 313.29 ± 64.78 mln/ml. More than half of the tested samples with polyzoospermia had a concentration 250–300 mln/ml. Concentration of 450 mln/ml and more detected in 3 % of samples. The maximum total number of spermatozoa in the ejaculate in our study was more than 2 billion sperm cells and was observed in two polyzoospermic men. One of these patients had the maximum concentration (615 mln/ml) also. We found a high correlation (r = 0.89; p < 0.01) between the volume of ejaculate and the total number of spermatozoa. Immature germ cells from ejaculate were estimated in 7 patients. There was a partial spermatogenesis arrest at meiosis I prophase in 5 out 7 of the examined semen samples.

The spatial organization of an eukaryotic genome plays an important role in the control of nuclear gene expression. The new Hi-C method allows investigation of the three-dimensional architecture of whole genomes. It has not been applied to study of the spatial configuration of a germ cell genome hitherto. Here we describe a protocol for production and quality control of Hi-C libraries from fibroblasts and sperm cells. Our results demonstrate that the Hi-C method can be used for studying the spatial organization of the densely packed sperm genome.

Molecular profiling of tumors may provide promising options for personalized treatment. We have examined the spectrum of germline and somatic mutations in 23 breast cancers (ВС) of various molecular subtypes, including tumors 1) with expression of estrogen, progesterone and/or epidermal growth factor receptor HER2/neu, and 2) with a triple negative phenotype. Genomic DNA specimens were isolated from archived tumor and normal tissue samples and subjected to targeted sequencing of the coding regions of 25 cancer-associated genes with a mean coverage of x 1000. In the triple negative subtype of ВС, the pathogenic germline mutations BRCA1 c.66&#95;67delAG (185delAG) and BRCA1 c.3226&#95;3227AG (3347delAG) were detected, while the germline mutation BRCA2 658&#95;659del (886delGT) was found in patients with positive receptor staining. Mutations in BRCAl/2 were overrepresented by frequency (80%), pointing at common loss of heterozygosity affecting the normal allele. Somatic mutations in the TP53 gene were found in 7/10 (70%) patients with the triple negative subtype of ВС and in 3/13 (23%) in the group with positive receptor staining. Additionally, in both groups of patients, somatic mutations of the PTEN, MSH2, MSH6, and MUTYH genes were detected.

Drosophila protein GAGA (GAF) is a factor of epigenetic transcription regulation of a large group of genes with a wide variety of cellular functions. GAF is encoded by the Trithorax-like (Trl) gene, which is important for the formation of various organs and tissues at all stages of ontogenesis. In our previous works, we showed that this protein is necessary for the development of the reproductive system, both in males and females of Drosophila. Decreased expression of the Trl gene led to multiple disorders of spermatogenesis and oogenesis. One of the significant disorders was associated with massive degradation and loss of cells in the germline. In this work, we carried out a more detailed cytological study to determine what type of germ cell death is characteristic of Trl mutants, and whether there are disturbances or changes in this process compared to the norm. The results obtained showed that the lack of GAF protein causes massive germ cell death in both females and males of Drosophila, but this death manifests itself in different ways, depending on the sex. In Trl females, this process does not differ phenotypically from the norm. In the dying egg chambers, signs of apoptosis and autophagy were revealed, as well as morphological features that are characteristic of the wild type. In males, Trl mutations induce mass germ cell death through autophagy, which is not typical of Drosophila spermatogenesis, and has not been previously described, neither in the norm nor in other genes' mutations. Thus, GAF lack in Trl mutants leads to increased germ cell death through apoptosis and autophagy. Ectopic cell death and germ line atrophy are probably associated with impaired expression of the GAGA factor target genes, among which there are genes that regulate both apoptosis and autophagy., (Copyright © AUTHORS.)

Introduction: as shown in previous studies, mutations in the BRCA1/2 and CHEK2 genes are associated with worsened long-term results of the definitive treatment for localized prostate cancer (PCa)., Aim: to evaluate the prognostic value of germline BRCA1/2 and CHEK2 mutations on time to castration-resistance in patients with metastatic PCa (mPCa), receiving hormonal therapy in the first-line systemic treatment., Materials and Methods: A total of 76 patients with mPCa receiving hormonal therapy with luteinizing hormone-releasing hormone analogue (LHRHa) in N.N. Blokhin National Medical Research Center of Oncology were recruited in our prospective study. All patients were genotyped for germline mutations in the BRCA1/2 and CHEK2 genes by real-time polymerase chain reaction using a set "OncoGenetics" (LLC "Research and Production Company DNA-Technology", Russia, registration certificate No 2010/08415) and the Sanger sequencing using a set "Beckman Coulter enomeLab GeXP". In addition, a histologic grade and volume of metastatic disease were evaluated., Results: Pathogenic and possibly pathogenic mutations in the BRCA2 and CHEK2 gene were identified in 19 (25%) patients. No cases of BRCA1 mutations were detected. Median time to castration resistance was significantly lower in BRCA2 and CHEK2 mutation carriers (7.93 mo, 95% confidence interval (CI) 2.62-13.25), than in non-carriers (48,66 mo, 95% CI 31.05-68.26, p<0,001). Cox analysis confirmed three independent unfavorable prognostic factors., Discussion: The results of our study and other publications have confirmed limited efficacy of standard approach to treatment hormone-sensitive mPCa in germline mutation BRCA2 and CHEK2 carriers. However, the main objective of studies was to assess the survival rates in these patients at the stage of castration-resistant mPCa., Conclusion: Our results demonstrated that germline BRCA2 and CHEK2 mutations are independent unfavorable predictors in patients with mPCa which are associated with decreased time to castration resistance (HR 3.04, 95% CI 1.63-5.66, p<0.001), particularly in subgroup with low volume metastatic disease (HR 4.59, 95% CI 2.06-10.22, p<0,001). An evaluation of a prognostic value of mutations in other DNA repair genes requires additional research.

In haploid and diploid organisms of the plant kingdom, meiotic division of diploid cells proceeds in two consecutive stages, with DNA replicating only once. In amphihaploids (interspecific or iontergeneric hybrids), where homologs are absent, the reduction of the chromosome number does not occur, meiosis is abnormal, and the plants are sterile. Gamete viability in F1 hybrids is ensured by a single division when chromosomes are separated into sister chromatids in either the first or the second division. Such gametes ensure partial fertility of amphihaploids, thereby facilitating their survival and stabilization of the polygenome. The frequency of the formation of viable gametes varies from a few cases to 98.8% in different anthers of the hybrids. Here, studies on the cytological mechanisms and genetic control of chromosome unreduction or restitution in different amphihaploids of the tribe Triticeae are reviewed. The current notions on the control of formation of restitution nuclei based on the principles of a prolonged metaphase I and different types of meiocytes. The main terms used for systematization of restitution mechanisms are first-division restitution (FDR), single-division meiosis (SDM), and unreductional meiotic cell division (UMCD). It has been assumed that archesporial cells of remote hybrids may have two cell division programs, the meiotic and the mitoyic ones. The possible approaches to the analysis of the genetic control of chromosome restitution in amphihaploids are discussed.

In this study, quantitative analysis of paternal genome inheritance by a hybrid form Rana "esculenta" (= Rana esculenta L., 1758 x Rana ridibunda Pall., 1881) (Amphibia, Ranidae) was examined. The hybrid form examined was characterized by a polymodal mode of inheritance (genome of any of the parental species can be inherited). The absence of correlation between the proportion of normal gametes and either sex or ploidity of the producer was demonstrated. The gametes produced could be both haploid and diploid (hybrid or homozygous). The mechanism of alloploid reproduction is discussed.

Migration and gametic structure have been analyzed in rural population of Sakha Republic (Yakutia). The populations studied differ from one another in the migration rate and direction, which are determined by the socioeconomic development of the regions and ethnic composition of settlements. A high rate of long-distance migrations and a low rate of migrations within uluses (districts) are characteristic of regions with well-developed industry and transportation and are more characteristic of immigrant than indigenous populations. In rural regions, migrations within uluses are more prevalent. The gametic structure of the youngest age group does not always correspond to the migration activity of previous generations. The migration effectiveness values (the correspondence of migration flows to the gametic structure depending on the geographic origin of the gametes) are different for men and women.

Genetic characteristics of intratetrad mating, i.e., fusion of haploid products of one meiotic division, are considered. Upon intratetrad mating, the probability of homozygotization is lower than that upon self-fertilization, while heterozygosity at genes linked to the mating-type locus, which determines the possibility of cell fusion, is preserved. If the mating-type locus is linked to the centromere, the genome regions adjoining the centromeres of all chromosomes remain heterozygous. Intratetrad mating is characteristic of a number of fungi (Saccharomyces cerevisiae, Saccharomycodes ludwigii, Neurospora tetrasperma, Agaricus bisporus, Microbotrium violaceum, and others). Parthenogenetic reproduction in some insects also involves this type of fusion of nuclei. Intratetrad mating leads to the accumulation of haplolethals (i.e., lethals manifesting in haploid cells but not hindering their mating) in pericentric chromosome regions. Since heterozygosity increases viability of an organism, recombination has been suppressed during evolution in fungi characterized by intratetrad mating, which ensures heterozygosity of the most part of the genome.

Estimation of gametic frequencies in multilocus polymorphic systems based on the numerical distribution of multilocus genotypes in a population sample ("analysis without pedigrees") is difficult because some gametes are not recognized in the data obtained. Even in the case of codominant systems, where all alleles can be recognized by genotypes, so that direct estimation of the frequencies of genes (alleles) is possible ("complete data"), estimation of the frequencies of multilocus gametes based on the data on multilocus genotypes is sometimes impossible, whether population data or even family data are used for studying genotypic segregation or analysis of linkage ("incomplete data"). Such "incomplete data" are analyzed based on the corresponding genetic models using the expectation-maximization (EM) algorithm. In this study, the EM algorithm based on the random-marriage model for a nonsubdivided population was used to estimate gametic frequencies. The EM algorithm used in the study does not set any limitations on the number of loci and the number of alleles of each locus. Locus and alleles are identified by numeration making possible to arrange loops. In each combination of alleles for a given combination of m out of L loci (L is the total number of loci studied), all alleles are assigned value 1, and the remaining alleles are assigned value 0. The sum of zeros and unities for each gamete is its gametic value (h), and the sum of the gametic values of the gametes that form a given genotype is the genotypic value (g) of this genotype. Then, gametes with the same h are united into a single class, which reduces the number of the estimated parameters. In a general case of m loci, this procedure yields m + 1 classes of gametes and 2m + 1 classes of genotypes with genotypic values g = 0, 1, 2, ..., 2m. The unknown frequencies of the m + 1 classes of gametes can be represented as functions of the gametic frequencies whose maximum likelihood estimations (MLEs) have been obtained in all previous EM procedures and the only unknown frequency (Pm(m)) that is to be estimated in the given EM procedure. At the expectation step, the expected frequencies (Fm(g) of the genotypes with genotypic values g are expressed in terms of the products of the frequencies of m + 1 classes of gametes. The data on genotypes are the numbers (ng) of individuals with genotypic values g = 0, 1, 2, 3, ..., 2m. The maximization step is the maximization of the logarithm of the likelihood function (LLF) for ng values. Thus, the EM algorithm is reduced, in each case, to solution of only one equation with one unknown parameter with the use of the ng values, i.e., the numbers of individuals after the corresponding regrouping of the data on the individuals' genotypes. Treatment of the data obtained by Kurbatova on the MNSs and Rhesus systems with alleles C, Cw, c, D, d, E, e with the use of Weir's EM algorithm and the EM algorithm suggested in this study yielded similar results. However, the MLEs of the parameters obtained with the use of either algorithm often converged to a wrong solution: the sum of the frequencies of all gametes (4 and 12 gametes for MNSs and Rhesus, respectively) was not equal to 1.0 even if the global maximum of LLF was reached for each of them (as it was for MNSs with the use of Weir's EM algorithm), with each parameter falling within admissible limits (e.g., [0, min(PN,Ps)] for PNs). The chi 2 function is suggested to be used as a goodness-of-fit function for the distribution of genotypes in a sample in order to select acceptable solutions. However, the minimum of this function only guarantee the acceptability of solutions if all limitations on the parameters are met: the sum of estimations of gametic frequencies is 1.0, each frequency falls within the admissible limits, and the "gametic algebra" is complied with (none of the frequencies is negative).

Materials have been generalized that were accumulated in population-ontogenetic studies of plants and leading features of the ontogeny of plants have been noted that determine specific structural features of their populations. The described patterns allowed the authors to develop simulation models of plant population dynamics. The results of simulation are provided, and they are compared to the empirical data. Problems have been considered that concern the influence of specific features of development of different plant biomorphs on the genetic structure of populations and biocoenotic processes.

Monosomic analysis revealed that a gametocidal gene in a common wheat line derivative from Aegilops speltoides is located on chromosome 2B. This gene induces semisterility, low level of chromosome breaks, shriveled seeds, and endosperm degeneration. The obtained data indicate that the localized gene is allelic to well known gametocidal genes Gc1a and Gc1b.

Distributions and gametic associations of HLA I antigens were studied in two Finno-Ugrian populations of Russia: Mordovians (300 subjects, including 148 Erzyas and 152 Mokshas) and Maris (137 subjects). Regarding the Mordovian population, Erzya and Moksh subpopulations significantly differed from each other only in the frequency of the A9 antigen. However, the Mari and Mordovian populations differed from each other considerably. Maris exhibited higher frequencies of antigens A9, B27, and B40 and lower frequencies of B5, B8, and B16 compared to Erzyas, as well as higher frequencies of A3, A28, B27, and B40 and lower frequencies of A10, B5, B8, B16, and B18 compared to Moksha. In addition, Erzyas, Mokshas, and Maris differed from one another in the gametic associations revealed. In general, our data indicated that the three populations, which display characteristic features of both Caucasoid and Mongoloid races, differ from one another with respect to the HLA genetic polymorphism. In all of the three populations, a positive association of the B27 antigen with spondylarthropathies (SAPs) was revealed. This confirms the hypothesis that B27 is involved in the pathogenesis of some rheumatoid diseases.

It has been demonstrated that heat resistance (and radiosensitivity) of the germ cells at all stages of oogenesis in the females of heat resistant drosophila line (T) is being formed during ontogenesis and depends on the environmental temperature. These characteristics were retained at the stage of imago, even in the cases of temperature changes (from +32 to +25 degrees C, or from +25 to +32 degrees C). The intensity of induced mutagenesis (by X-rays and high temperature) which was evaluated for the frequency of dominant lethal mutations and X-chromosome loss depended on the temperature during development, but depends on no temperature at the time of treating imago with the mutagenic agents. It is suggested to be a result of the participation of heat shock proteins in repair of DNA damages.

The discovery of the gametic imprinting phenomena in mammals makes it possible to have a new look at some facts concerning the expression and inheritance of genes with variable penetrance. Fused (Fu) is a dominant mutation located on chromosome 17, one of the few examples uses to demonstrate gametic imprinting in mice. This mutation has maternal effect connected with decrease in its penetrance. It was shown that t12 haplotype significantly reduces penetrance of the Fu in the progeny of Fu/t12 females. The results of reciprocal crosses of heterozygotes for t12 haplotypes indicate that penetrance of maternal Fu gene is reduced. Far more strong influence on the fused penetrance have the dominant suppressors, located beyond the chromosome 17. The penetrance of the fused gene decreases in that case up to 8-17%. Results of the experiments show strong influence of gametic pathway on penetrance of the gene by which the gene is transmitted to the next generation. The results also made it possible to describe the regularities of gametic imprinting. This phenomenon clearly indicates the existence of gametic and zygotic ontogenetic phases. According to the hypothesis proposed gametic phase of ontogenesis in mammals starts after initialization, i. e. after a process of chromosome erasing from epigenetic information and preparing to enter the next ontogenetic cycle.