Prader-Willi Syndrome is primarily caused by a deficiency in which chromosomes?

Prader-Willi Syndrome is primarily associated with abnormalities in chromosome 15. This genetic disorder is often the result of the deletion of a segment of paternal chromosome 15 or the absence of expression of genes within this region due to genomic imprinting. This deficiency leads to various symptoms, including hypotonia, obesity, intellectual disability, and specific behavioral problems.

In the context of the other options, chromosomes 13, 21, and 23 do not play a direct role in the development of Prader-Willi Syndrome. Chromosome 13 is linked to other genetic disorders such as Patau syndrome, chromosome 21 is notably associated with Down syndrome, and chromosome 23 relates to sex chromosomes and determines gender rather than being directly implicated in Prader-Willi Syndrome. Understanding the significance of chromosome 15 helps clarify the genetic underpinnings of this condition.