Department of Biotechnology of Reproduction, Immuno- and Cytogenetics, National Research Institute of Animal Production, Krakowska 2, 32-083 Balice n. Krakow, Poland. majawrzeska@wp.pl
In contrast to the biallelic expression of most genes, expression of imprinted genes is monoallelic and depends on the sex of the transmitting parents. In humans it has been implicated in some developmental failures, neurodevelopmental and neurobehavioral disorders (such as Prader-Willi/Angelman, Silver-Russel or Beckwith-Wiedemann syndromes). The aim of this review is to present the phenomenon of parental imprinting as well as its molecular mechanism in various mammals. Several maternal and paternal imprinted genes and gene clusters are described.