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XXYY syndrome is a sex chromosome anomaly in which males have two extra chromosomes, one X and one Y chromosome. Human cells usually contain two sex chromosomes, one from the mother and one from the father. Usually, females have two X chromosomes (XX) and males have one X and one Y chromosome (XY).
XXYY syndrome occurs in approximately 1:18,000–1:40,000 males. Although the physical phenotype is similar to 47,XXY (tall stature, hypergonadotropic hypogonadism, and infer-tility), XXYY is associated with additional medical problems and more significant neurodevelopmental and psychological features.
XXYY Syndrome is the name attached to the cluster of symptoms that arise as a result of the 48,XXYY chromosome pattern. It affects one in every 17,000 boys.
48,XXYY syndrome results from nondisjunction events of sex chromosomes primarily during spermatogenesis (meiosis I and/or meiosis II) or less often from post-zygotic mitotic nondisjunction during cell division.
XXYY syndrome is the result of having extra copies of both the X and Y chromosomes, occurring when a normal female oozyte (X m) is fertilized with an aneuploidy sperm (X p Y p Y p) produced from double nondisjunction during meiosis.
48,XXYY syndrome results from a nondisjunction event of sex chromosomes during spermatogenesis or, less often, from post-zygotic mitotic nondisjunction during cell division. There are no known predisposing factors.
