The concept of Prader Willi Syndrome in this paragraph and what is maternal uniparental disomy?

the concept of Prader Willi Syndrome in this paragraph and what is maternal uniparental disomy??

Normally the gene should contain two alleles one from mother and one from father

In prader willi syndrome i.e occuring in chromosome 15q11

The maternal allele is silenced or non functional due to lower expression of genes or epigenetics and with that there occurs deletion of the paternal allele also thus leading to prader will ( this is the deletion cause)

Now coming to uniparental disomy which means one parent is contributing both the alleles so here the non functional mother alleles are present only leading to prader willi

Uniparental disomy= one parent contributing both the alleles