The word imprinting may sound like something you've heard on CSI, but it's actually a form of epigenetics. Even though two copies of a given gene are inherited, one from mom and one from dad, in certain circumstances, one is permanently turned off. The non-expressed one is said to be imprinted. As of now, we know of at least 80 genes that are imprinted by epigenetic markers, causing them to be active or inactive in the offspring based on parent of origin.
In general, expressed genes that are inherited from the mother conserve maternal resources and limit fetal growth, while expressed genes that are inherited from the father promote fetal growth, even at the expense of the mother. Problems can occur when genes that are supposed to be imprinted, or turned off, are not, or when the wrong parent's gene is imprinted. The gene for insulin-like growth factor 2 (IGF2) is normally turned on from the father and off from the mother. If the mother's copy is not turned off, the child can develop Wilms tumors of the kidney. Loss of imprinting of the mother's IGF2 gene later in life can contribute to age-related cancers, including cancer of the prostate and colon.
Find out more about this book:YOU: Having a Baby: The Owner's Manual to a Happy and Healthy Pregnancy