Genomic imprinting results in the deliberate silencing of alleles, dictated by their parental origin, but reversible on passage through the germ line. In this chapter, we shall consider the functional properties of imprinted genes, why these genes might have been singled out for the risky strategy of mono-allelic expression, and how imprinting is regulated. We shall look at how imprinted genes affect processes throughout our lifetimes, from the way we grow in the womb to the control of metabolism as adults. In contrast to the depth of our knowledge ofthe contributions of imprinted genes to growth of the fetus, our understanding of their roles in adult physiology is still rather poor. We shall look at those imprinted genes that have been implicated in diabetes and those which are known to help determine (3-cell mass. It is likely that the effects of imprinted genes on these processes are more pervasive than currently recognised. The intention of this chapter is therefore to equip the readers with the general principles governing imprinting, so that they are able to comprehend this intriguing and important form of gene regulation when they encounter it next.
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