GENE IMPRINTING (silencing) and HUMAN HEALTH...
                                                                             genetically predisposed to a health problem.

In organisms that exhibit live birth each offspring inherits one copy of a gene from mom and a second allele from dad, but GENE IMPRINTING can results in some alleles being “switched off”. Gene imprinting occurs when certain alleles of particular genes function differently depending on whether they are inherited from the paternal or maternal parent. With only one functional allele being present in the offspring, there is no backup, if that copy goes bad during a life span, that makes the individual more vulnerable to genetic diseases.

Dr. Randy Jirtle’s research team at Duke have identified some 200 of these “silenced genes,” which may play a real role in human health and how the environment — food, stress, pollution — can interact with genes to help determine why some people get sick and others do not. The list of “imprinted” genes was published online Friday by the journal Genome Research.

Usually, people inherit a copy of each gene from each parent and both copies are active, programmed to do their jobs whenever needed. For some genes, people inherit an active copy only from the mother or only from the father. If one copy of a gene becomes mutated and quits working properly, often the other copy could compensate. But, when genes go awry. possible as individuals or are influenced by environmental factors, the genetic imprinting has knocked out that backup. Molecular signals tell, or “imprint,” the copy from the other parent to be silent. You could compare it to flying a two-engine airplane with one engine cut off. If the other engine quits, the the plane crashes. In genetic terms, if one tumor-suppressing gene is silenced and the active one breaks down, a person is more susceptible to cancer.

Using DNA sequences whose patterns pointed to the presence of imprinted genes instead of active ones, Jirtle’s team searched the Human Genome Databases. Many of the imprinted genes they found are in regions of chromosomes already linked to the development of obesity, diabetes, cancer and some other major diseases. For example, one of the imprinted genes appears to prevent bladder cancer and a second appears to play a role in causing various cancers and may affect epilepsy and bipolar disorder.

Researchers now can begin to ask questions as: How behavioral or environmental factors may tip the balance for someone who is genetically predisposed to a health problem?  and how imprinting may be changed to reactivate an imprinted gene after birth.

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