If the microdeletion on chromosome 15 that causes Prader-Willi syndrome originates from the mother, which syndrome results?

The key to understanding this question lies in the genetic basis of Prader-Willi syndrome and its relationship with Angelman syndrome. Both conditions are associated with abnormalities on chromosome 15, but they have different causes depending on the parent of origin.

Prader-Willi syndrome is typically caused by a deletion of paternal genes on chromosome 15. When the microdeletion occurs in the paternal chromosome, it results in the clinical features of Prader-Willi syndrome, which include hyperphagia, obesity, developmental delays, and hypogonadism.

In contrast, if the deletion on chromosome 15 originates from the mother, the result is Angelman syndrome. This syndrome is characterized by intellectual disability, severe speech impairment, ataxia, and a happy demeanor with frequent laughter. Angelman syndrome occurs due to the absence of expression of the maternal allele on chromosome 15 due to the inherited deletion, highlighting the phenomenon of genomic imprinting where certain genes are expressed depending on their parent of origin.

Therefore, when a microdeletion on chromosome 15 results from the mother, it leads to Angelman syndrome, making this option the correct answer. The other options listed do not relate to this particular genetic mechanism or the specific syndromes associated with chromosome 15 delet