Fragile x - Fragile x-syndrome Fragile-x syndrome is the...

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Fragile x-syndrome Fragile-x syndrome is the most common genetic cause of learning difficulties after Down's syndrome. It is caused by a dominant X-linked gene with a penetrance of only 50% in females. It results due to a triplet repeat on the X chromosome. Epidemiology Incidence = 1/3500 Males are predominantly affected although females may still have symptoms. Mothers are carriers ( i.e. , are conclusively proven to be carriers) if a male child is affected, but not necessarily if female children are affected, as a female child with one fragile and one normal X-chromosome may have inherited the fragile chromosome from their father. Clinical features Aside from intellectual disability, prominent physical characteristics of the syndrome include: Elongated face Protruding ears Flat feet, Macroorchidism (larger testes) High-arched palate (related to the above) Hyperextensible finger joints Double-jointed thumbs Low muscle tone Behavioural characteristics may include:
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This note was uploaded on 12/04/2011 for the course ANTHRO 2000 taught by Professor Monicaoyola during the Fall '10 term at Broward College.

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Fragile x - Fragile x-syndrome Fragile-x syndrome is the...

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