question

[qshyrn]

 in Nature of Biology p.296, the sentence Just before the title "A
case of Down SYndrome" says: "Angelman syndrome, characterised by poor
motor coordination and mental retardation, can result if an embryo
inherits both of its no.15 chromosomes from its mother and none from
its father".... I dont really get this. Why would the embryo have a
genetic disorder? its still got 2 normal no.15 chromosomes from its
mother.... (which arent sex chromosomes) ..

[n.f]

I've had a look around and found this: http://ghr.nlm.nih.gov/chromosome=15
The UBE3A gene located on chromosome 15 will be inactive in the brain causing Angelman syndrome.
From what I've read though there aren't any cases of inheriting both no. 15 chromosomes from the mother (which you can read below the Angelman syndrome; Prader-Willi syndrome)
Inheriting two chromosomes from one parent is known as uniparental disomy: http://en.wikipedia.org/wiki/Uniparental_disomy