Prader-Willi syndrome is caused by a missing gene on chromosome 15. Normally, parents each pass down a copy of this chromosome. The defect can occur in a couple of ways: The father's genes are missing on chromosome 15.
: easy for the mind to understand or recognize. 1  It was obvious that things weren't working out. 2  Her reasons for leaving were obvious. = It's obvious why she left. 3  The answer seems obvious enough to me.  The problem was immediately obvious to everyone in the 1  room. He was the obvious candidate/choice for president.
visible. 1  Possible to see; perceptible to the eye: a visible object. 2  a. Obvious to the eye: a visible change of expression. b. Being often in the public view; conspicuous. 3  Manifest; apparent: no visible solution to the problem. 4  On hand; available: a visible supply.