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.

Is this case caused by a deletion in the paternal copy of chromosome 15? Explain.

Verified step by step guidance

1. Identify the lanes in the gel image: Lane 1 corresponds to the father, Lane 2 to the affected child, Lane 3 to the mother, Lane 4 to a sibling, and Lane 5 to another sibling.
2. Observe the band patterns in each lane. Each band represents an allele of the STR region on chromosome 15.
3. Compare the band pattern of the affected child (Lane 2) with the parents (Lanes 1 and 3).
4. Check if the affected child has inherited one band from each parent. If the child has only bands matching the mother and none from the father, it suggests uniparental disomy or a deletion.
5. Determine if the paternal band is missing in the affected child. If the child has only maternal bands, it indicates a deletion in the paternal chromosome 15.