In this article in The Scientist, “Imprinting Diversity”, Cristina Luiggi interviews Joachim Messing about ways in which genomic imprinting may be a strong driver of diversity:
Sexual reproduction yields offspring with two copies of the same gene, one from each parent; but in an epigenetic phenomenon known as genomic imprinting, only one copy of certain genes is turned on or off, depending on which parent contributed it. Imprinted genes are stamped by patterns of DNA methylation or histone modification during gamete formation, and their activation or inactivation is then passed on to offspring. Previously, approximately 100 genes were thought to be imprinted in mammals. But Rutgers University molecular biologist and F1000 Member Joachim Messing, discusses a recent paper that found many more imprinted genes in mammals, suggesting this may be a major form of epigenetic regulation (Science, 329:643-48, 2010).
But get this:
Joachim Messing: The genes that were initially discovered to be imprinted in mammals were those that had an influence on the development of the embryo. So that led to the hypothesis that there are competing interests between the two parents in the offspring, and that only genes having to do with a conflict of interests between the two parents are imprinted. The female has to balance the allocation of resources between herself and her offspring, while the male wants the resources to go primarily to the offspring. From a selection point of view, the male sperm will promote the growth of the offspring, whereas the female has to be able to reproduce more often, so she has to be careful in allocating the resources.They discovered that there are not just a handful of genes that might play a role in growth—there are more than a thousand genes that are implicated in parental imprinting. So it may have nothing to do with this conflict theory.