Gametic imprinting as a speciation mechanism in mammals

Gametic imprinting renders mammalian male and female genomes functionally hemizygous at specific loci. Successful embryogenesis can only be accomplished in the presence of both parental genomes. The mechanism of gametic imprinting is at present unknown, although circumstantial evidence suggests it is similar in nature to X inactivation. A model is presented which describes the effects of switching the imprint pattern at male and female target genes. The consequence of such an event is reproductive isolation, and could lead to the formation of a new species.