lect 29 Prader-Willi & Angelman Syndromes Lecture Review

This flashcard set covers the clinical features, genetic mechanisms, and diagnostic methods for Prader-Willi and Angelman syndromes, focusing on chromosome 15 imprinting and uniparental disomy.

Prader-Willi syndrome

A genetic condition characterized by neonatal hypotonia, developmental delay, childhood hyperphagia, obesity, and the loss of the paternal allele expression in the $15q11-q13$ region.

Angelman syndrome

A genetic condition characterized by intellectual disability, a happy disposition, seizures, and the loss of the maternal allele expression in the $15q11-q13$ region.

Hyperphagia

A clinical feature of Prader-Willi syndrome developed during childhood involving excessive or uncontrollable eating.

Neonatal hypotonia

Low muscle tone observed in newborns, a common clinical feature of Prader-Willi syndrome.

Genomic Imprinting

A normal process regulated during gametogenesis where one allele of a gene is switched off or silenced depending on its parental origin.

Methylation

The mechanism that causes transcription to be switched off at CpG islands associated with promoters to achieve gene imprinting.

SNRPN

Small Nuclear Ribonucleoprotein Polypeptide N; a gene on chromosome 15 that is normally only expressed from the paternal allele.

UBE3A

Ubiquitin-Protein Ligase E3A; a gene on chromosome 15 that is normally only expressed from the maternal allele, specifically in brain tissue.

Imprinting Centre (IC)

A bipartite locus located upstream of $SNRPN$ and $UBE3A$ on chromosome 15 that controls the imprinting status of the region.

Uniparental Disomy (UPD)

The inheritance of two homologous chromosomes from one parent rather than one from each parent.

Heterodisomy

A form of UPD where an individual inherits two different homologous chromosomes from a single parent.

Isodisomy

A form of UPD where an individual inherits two copies of the exactly same homologue from a single parent.

Trisomy Rescue

A mechanism for UPD where a trisomic conceptus loses one homologue to return to a disomic state, potentially resulting in maternal or paternal UPD.

Monosomy Rescue

A mechanism for UPD where a monosomic conceptus duplicates its single chromosome, resulting in uniparental isodisomy.

MS-MLPA

Methylation-sensitive Multiplex Ligation-dependent Probe Amplification; a diagnostic laboratory technique used to detect deletions and UPD defects.

Ataxia

A clinical feature of Angelman syndrome involving a lack of muscle coordination during voluntary movements.

Hypogonadism

A clinical feature of Prader-Willi syndrome involving diminished functional activity of the gonads.