Genomic imprinting describes the epigenetic phenomenon is that the parent's origin is marked on genome. The phenomenon is unique to placental mammals, and causes parent-of-origin-specific monoallelic expression of most of imprinted genes. The previous studies on mice clarified that these gene expression control required the sex-specific differences of DNA methylation which were established in oogenesis or spermatogenesis. In this paper, we review the relevance of genomic imprinting mechanism and DNA methylation.

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Balanced carriers of chromosome structural abnormalities, although phenotypically normal, may present with reduced fertility, recurrent miscarriages, or offspring with an abnormal phenotype. While balanced translocations are found in 0.35% of neonatal population, they occur in 1.4% of IVF patients with implantation failure and 2% of patients with recurrent miscarriages. At meiosis I, translocated chromosomes are paired with their corresponding normal chromosomes and form a quadrivalent (in the case of reciprocal translocation) or a trivalent (in the case of Robertsonian translocation). The unbalanced gametes are produced through malsegregation of these unique complexes. The occurrence risk of the unbalanced gametes depends on the number and the breakpoints of the chromosomes involved in translocation, and the extent of the genetic imbalance resulting from abnormal segregation could determine the viability of the gamete or the conception. Recently, PGD (preimplantation genetic diagnosis) has been performed worldwide for translocation carriers in order to select embryos with no genetic imbalance and increase their pregnancy and delivery rates. Although there is a possibility of successful natural outcome in many translocation carriers, the introduction of PGD into ART is expected to improve reproductive performance of these couples.

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Recent studies have indicated increased imprinting defects in children born after assisted reproductive technology (ART). The developmental mechanisms are unknown but the Beckwith-Wiedermann syndrome (BWS) and Angelman syndrome (AS) are recognized as imprinting aberration syndromes related to ART. It is also likely that another imprinting aberration syndrome, the Silver-Russell syndrome (SRS), is related to ART. Consideration about the genetic risk of ART is an important matter, and we must examine the association of ART with the occurrence of abnormal imprinting.

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When using animals in experiments, it is important to select the animal that best suits the experiment's purpose. Because non-human primates are closely related to humans, they are invaluable for use in clinical trials. Researchers using non-human primates should understand their characteristics before the start of the study and must execute the experiments efficiently. This article summarizes reproductive manipulation techniques in the study of non-human primates and the current status of this research.

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Japan Society of Mammalian Ova Research (JSMOR) aimed at improvement of quality of the embryologist engaged in assisted reproductive technology (ART) to have a large role for infertility treatment and started an authorization system of embryologist in JSMOR from April, 2002. We analyzed it about 455 embryologists whom we authorized as the embryologist of ART till now. A woman accounted for 78.7% in sexuality. By age distinction, the range of 25-29 years old was the most (43.3%). By analysis of last educational background of an embryologist, a graduate of university accounted for most 37.1%. The embryologist who acquired a degree was 18.9%. One to two years of the engagement period in the ART laboratory was the most (43.1%). The duty area had most Kanto area (31.9%). A type of duty institution was the most clinics (60.6%). The actual situation of embryologist became clear by this report. Embryologist deals with gamete and embryo directly and requires are much knowledge of ART, trained skill, high ethicality and dignity. A public authorization system is good for such embryologist. It is thought that an authorization system leads to improvement of social status of embryologist.

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