Prader-Willi syndrome is caused by the deletion of the paternal copy of a small section of human chromosome 15. In normal individuals, only the paternal copies of the genes in this section of chromosome 15 are expressed; the maternally inherited copies of these genes are silent due to maternal imprinting. In patients carrying the deletion on chromosome 15 cannot be expressed and the individuals have the Prader-Willi phenotype. Assuming that Prader-Willi syndrome is 100% penetrant, answer the following questions:
A) What proportion of the children of an affected male will have the Prader-Willi phenotype? Explain.
B) What proportion of the children of an affected female will havae the Prader-Willi phenotype? Explain.