Correct option is B
The correct answer is: (2) Maternal uniparental disomy
Explanation:
Prader-Willi syndrome (PWS) occurs when there is a lack of functional genes on the paternal copy of chromosome 15. In cases of maternal uniparental disomy (UPD), both copies of chromosome 15 are inherited from the mother, which results in a lack of paternal gene expression. Since the paternal copy of chromosome 15 is essential for normal development and function, its absence leads to the characteristics of Prader-Willi syndrome. In this case, the syndrome results from inheriting both chromosome 15s from the mother, causing a loss of the paternal genes needed for normal development.
Information Booster:
Prader-Willi syndrome is a genetic disorder caused by a lack of functional genes from the paternal chromosome 15.
Maternal uniparental disomy results in both copies of chromosome 15 coming from the mother, which leads to the loss of paternal genetic material.
Features of Prader-Willi syndrome include hypotonia, developmental delays, obesity, and hyperphagia (increased appetite).
Prader-Willi syndrome can also result from deletions of the paternal 15q11-q13 region or from imprinting defects.
In imprinting disorders, the expression of certain genes depends on whether they are inherited from the mother or the father.
Maternal uniparental disomy is one mechanism that leads to the disorder, while other causes include paternal deletions or imprinting defects.
Additional Information:
Option (1) Paternal uniparental disomy: This is incorrect for Prader-Willi syndrome. Paternal uniparental disomy would cause Angelman syndrome, a different disorder, because it leads to the absence of the maternal genes on chromosome 15.
Option (3) Imprinting of 15q11-q13 locus in maternal copy: This is related to Angelman syndrome. Imprinting defects on the maternal chromosome 15 lead to the characteristics of Angelman syndrome, not Prader-Willi syndrome.
Option (4) Imprinting of 15q23-q25 locus in paternal copy: This is not a typical cause of Prader-Willi syndrome. Imprinting defects on the paternal chromosome 15, particularly in the 15q11-q13 region, lead to Prader-Willi syndrome, but this specific locus (15q23-q25) is not commonly associated with the disorder.
