IMPRINTED GENES AND REGULATION OF GENE-EXPRESSION BY EPIGENETIC INHERITANCE

Six new imprinted genes have recently been identified by association w ith established imprinted regions, in systematic screens or by serendi pity. This brings the total to seventeen imprinted genes, which displa y a wide variety of functions. Some imprinted genes have been shown to be both physically and mechanistically linked within domains that are under the control of an imprinting centre. Others may apparently unde rgo imprinting independently. Methylation is clearly required for main tenance of mono-allelic expression while chromatin structure and non-c oding RNAs may also play a role.