fragile x syndrome - bergkamp

[ArchivalUser]

..is it sex linked recessive or sex linked dominant?

[ArchivalUser]

x linked recessive.

[ArchivalUser]

it is xr
but roughly around 60% of carriers are symptomatic so some geneticits consider it to be xd
it is xr according to most sources it is the commonest mendelian disorder to cause mental retardation it is the second most common genetic source of mr
it exhibits triplet repeat
and the phenomenon of anticipation
xd diseases are familial hypophosphatemia
rett syndrome incontentia pigmenti ,alport, orodigitalfacial

[ArchivalUser]

in kaplan biochem it`s given as sxd, though goljan has mentioned it as sxr..u sure mate?

[ArchivalUser]

thanks tec and drguru, what is orodigitalfacial?

[ArchivalUser]

in fa its X R
dont know about other sources.

[ArchivalUser]

ya in biochemits writen as x d

[ArchivalUser]

Fragile X (and almost everything X-linked) is X recessive. As drguru said, only a few X-linked diseases are dominant (Goltz-syndrome, Incontinantia pigmenti, Hypophosphatemic rickets, Orofaciodigital syndrome), but of those X-linked dominant diseases I think they are just interested in us to know Hypophosphatemic rickets (also known as Vitamin D resistance rickets).

Fragile X syndrome is a recessive disease, but its inheritance has unusual features because of its multiple repeats of CGG, that causes anticipation (age of onset of disease is earlier in succeeding generation or its more severe). (Check BRS Path pag.52)