Genomic Imprinting: Epigenetic Control
| Concept | Molecular & Clinical Explanation |
|---|---|
| Definition | Expression of a gene depends on whether it is inherited from the mother or the father. It involves epigenetic silencing (typically methylation) of one parental allele. |
| Prader-Willi | Loss of paternal contribution to the 15q11-13 region (e.g., deletion). Presents with hyperphagia, obesity, intellectual disability, and hypogonadism. |
| Angelman | Loss of maternal contribution to the 15q11-13 region. Presents with seizures, ataxia, and “happy puppet” syndrome (frequent laughter). |
High-Yield Core Realities:
- Uniparental Disomy (UPD): Both copies of a chromosome are inherited from the same parent. This can cause imprinting disorders if the inherited chromosome is the one that is normally silenced.
- Mechanism of Silencing: DNA methylation (at CpG islands) and histone modification are the primary mechanisms that maintain the imprinted status through mitotic cell divisions.
- Resetting: Imprints are erased during gametogenesis and then “reset” according to the individual’s own biological sex, ensuring that offspring receive the appropriate maternal/paternal imprint.
- Clinical Resource: For deep-dive diagrams, high-yield summary tables, and practice questions on epigenetic regulation and imprinting, visit mymedschool.org.