Using a basic genetic difference between men and women, the Translational Genomics Research Institute (TGen) has uncovered a way to track down the source of a neurological disorder in a young girl. TGen's discovery relies on a simple genetic fact: men have one X and one Y chromosome, while women have two X chromosomes. This women-only factor was leveraged by TGen investigators to develop a highly accurate method of tracking down a previously unrecognized disorder of the X-chromosome. The study of a pre-teen girl, who went years with an undiagnosed neurobehavioral condition, was published online on December 13, 2014 in an open-access article in PLOS ONE. TGen's findings were made within its Dorrance Center for Rare Childhood Disorders, where investigators and clinicians apply the latest tools of genomic medicine to provide answers for parents seeking to identify the disease or disorder affecting their child. The scientists sequenced, or spelled out in order, the complete genetic codes of DNA and RNA of the girl. Because girls inherit an X chromosome from each of their parents (boys inherit a Y chromosome from their father), the scientists also sequenced the girl’s mother and father. On average, about half of all X chromosomes active in a female come from the mother and the other half from the father. "We now have the tools to significantly accelerate the diagnostic process, reducing the need for children to undergo multiple tests that can be emotionally and physically taxing for the entire family," said Dr. David Craig, TGen's Deputy Director of Bioinformatics, Co-Director of the Dorrance Center and the paper's senior author. Sequencing would reveal the proportion of X chromosomes, and if disproportionate, whether the more abundant of the two were damaged in some way, which often leads to X-linked genetic conditions.
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