Multiple choice

Prader-Willi syndrome (PWS) can result from either an interstitial deletion involving the paternal copy of chromosome subregion 15q1-q13 or from maternal uniparental disomy of chromosome 15. The reason for this is

  1. the maternal copy of the gene(s) credited for PWS applies a dominant negative effect of the paternal allele

  2. PWS is a consequence of an anomaly of X-chromosome inactivation

  3. the paternal copy of the gene(s) responsible for PWS is imprinted and is not signified

  4. the maternal copy of the gene(s) responsible for PWS is imprinted and is not signified
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Explanation

Prader-Willi Syndrome (PWS) is caused by genomic imprinting, defined as the differential expression of maternal and paternal alleles. When the information in region 15q11-q13 is derived only from a mother (either via uniparental disomy (both chromosomes from a single parent) or deletion on the paternal chromosome), the maternally imprinted chromosome is unable to express its genetic information and the result is PWS.

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