Prader–Willi syndrome (PWS) is a genetic disorder with a clinical profile of obesity, intellectual disability, and short stature. It can be caused in several ways. Most common is a deletion on the paternal copy of chromosome 15, but it can also be caused by an epigenetic imprinting disorder, and uniparental disomy, an event in which the affected child receives two copies of the maternal chromosome 15. A child with PWS comes to your clinic for a diagnosis of the molecular basis for this condition. The gel below shows the results of testing with short tandem repeats (STRs) from the region of chromosome 15 associated with the disorder.

Based on your interpretation of the data, what is the cause of PWS in this case? Explain your reasoning. 

Video transcript

Hey, everyone. Let's take a look at this question together. Broader Willi syndrome is a condition in which a region of chromosome 15 becomes unstable, thereby affecting gene expression regulation, which of the following cases will cause the occurrence of broader Willi syndrome. So when talking about Prada Willi syndrome, we know that the corresponding broader will the critical region of the mother in that chromosome 15 is always inactive, which means that most of the cases involves some kind of issues with the expression within the father. And so when we have the loss of father critical region, that means that we have no active jeans within that broader Willie critical region. And so this causes that broader Willi syndrome or P W S. And so looking at the falling cases, the one that will cause the occurrence of that Prada Willi syndrome is an issue with the father. So answer choice C is the correct answer because the father's Prouder Willie critical region in chromosome 15 getting deleted will mean that we have the loss of the father region and no active genes which causes Prouder Willi syndrome. So answer choice C is the correct answer. I hope you found this video to be helpful. Thank you and goodbye.