Genomic imprinting is a mechanism for regulating gene expression that allows expression of only one of the parental alleles, although both alleles are functional. Unlike most genes in which expression is biallelic, genes that are subjected to this mechanism (imprinted genes) have monoalelic expression; By definition, in an imprinted loci, only one allele is active (maternal or paternal), and the inactive is epigenetically marked by histonic modification and / or methylation of cytosines.
Genomic imprinting can cause some disturbances, among them Prader-Willi syndrome, which is a genetic disorder that involves a partial deletion of chromosome 15q on the paternal chromosome.
