Talk:BGDB Sexual Differentiation - Sex Determination

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BGD Internal Links 2009 Male/Female Practical 1. Sex Determination

1991 - The initiator of the X inactivation process was discovered (1991) to be regulated by a region on the inactivating X chromosome encoding an X inactive specific transcript (XIST), that acts as RNA and does not encode a protein. Furthermore X inactivation occurs randomly throughout the embryo, generating a mosaic of maternal and paternally derived X chromosome activity in all tissues and organs.



  • Fragile X mental retardation is characterized by moderate to severe mental retardation, macroorchidism, and distinct facial features, including long face, large ears, and prominent jaw. In most cases, the disorder is caused by the unstable expansion of a CGG repeat in the FMR1 gene and abnormal methylation, which results in suppression of FMR1 transcription and decreased protein levels in the brain (Devys et al., 1993).