This is because, if you have very good intelligence genes on your X chromosome, it pays not to have them muffled by more average genes on another X chromosome.
Your mother can give you only an X chromosome, but your father can pass on an X or a Y chromosome.
It's also referred to as 47, XXX syndrome because of the existence of a 47th chromosome, which is the extra X chromosome.
Because only some cells contain the extra X chromosome, females with the mosaic form of triple X syndrome may have less severe symptoms.
That meant the mutation was almost certainly on a gene on the X chromosome.
But boys have only one X chromosome, leaving them more vulnerable to defects like this.
In the mosaic form, only some of the body's cells have the third X chromosome.
If you receive an X chromosome from your father, the XX pair makes you genetically a female.
Red-green colorblindness is far more common in men than women because it's a recessive gene carried on the X chromosome.
Professor Mike Stratton, of the Wellcome Trust Sanger Institute, said that insights into harmful genes on the X chromosome might allow scientists to intervene to prevent the onset of mental retardation.
Sperm sorting can be carried out either by putting live sperm in a dense liquid and spinning it in a centrifuge to separate sperm carrying the x chromosome and those carrying the y chromosome.
See, for instance, this case I wrote about a year ago, or this one, in which sequencing the part of the exome that was on the X chromosome allowed scientists to figure out the cause of a genetic disease that was killing young boys in a Utah family.
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At the clinic, run by Dr. Geeta Shroff, a former obstetrician and pediatrician who admits she is self taught in the practice of stem cell medicine, Cash received embryonic stem cell injections for a disorder that resembles Down syndrome and is caused by a missing part of his X chromosome.
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And that those who paid the same ticket price, bought the same game or applied for the same job should not have to expect to get harassed and insulted, or quizzed incessantly on their credentials, until any risk that they might have had fun is destroyed, simply because their extra X chromosome makes them instantly a cause for suspicion.
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