Fragile X and Lesch-Nyhan syndromes are both caused by genetic abnormalities on the X chromosome. Explain the effects of these abnormalities for each disorder and discuss the prevalence rates among the sexes

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Answer 1

Fragile X syndrome (FXS) occurs when a DNA series makes too many copies of itself and "turns off" a gene on the X chromosome. When the gene is turned off, cells do not make a necessary protein, thus resulting in FXS. Symptoms of FXS include intellectual disability and behavioral disorders (e.g. hyperactivity, temper tantrums, irritability, and self-injurious behaviors). Perhaps because girls have 2 X chromosomes (that is, they have a "spare" X chromosome) they are only half as likely as boys to have FXS.
Lesch-Nyhan syndrome is a rare genetic disorder that is transmitted on the X chromosome. When the genetic defect is present, excess uric acid accumulates throughout the body. Lesch-Nyhan syndrome causes intellectual disability and behavioral problems (e.g., cognitive dysfunction, aggressive and impulsive behaviors, and persistent and severe self-injurious behaviors). Because it is a recessive trait, this disorder occurs only in boys.