Prader-Willi syndrome (PWS) is a complex neurodevelopmental genetic condition that was first described in 1956 by Prader and colleagues. The condition is characterised by a recognisable pattern of dysmorphic features as well as major neurological, developmental, behavioural and psychiatric differences.1-5
It has been highlighted that PWS should be referred to as a genomic condition rather than a genetic condition because of its genomic imprinting feature.1,4
The genotype of PWS
Each cell in the human body contains genetic material inside its nucleus in the form of chromosomes (the genotype); 23 pairs of chromosomes composed of two strands of DNA are linked together to form a double helix, with one chromosome from each pair being inherited from each parent.
The genes (segments of the DNA) provide the genetic code for specific amino acids, which in turn form specific proteins - the building blocks of the human body. Any disruption or changes to DNA may result in alterations to protein expression and function (the phenotype).
Normally the two copies of genes (one from each parent) are equally controlled, but for a small proportion of genes certain sections of the genome are only activated if they are inherited from a parent of a particular sex. Therefore, for some areas of the genetic material the maternally and paternally derived copies are controlled differently.