Preferential expression of the gene depending upon the parent of origin is called:

Impoant functional differences exist between the paternal allele and the maternal allele. These differences result from an epigenetic process called imprinting. In most cases, imprinting selectively inactivates either the maternal or paternal allele. Thus, maternal imprinting refers to transcriptional silencing of the maternal allele, whereas paternal imprinting implies that the paternal allele is inactivated. E.g. Prader-Willi syndrome and Angelman syndrome.