A study by scientists of Duke Universityhave identified ‘silenced genes’ which makes a person vulnerable to various disorders ranging from obesity to cancer. The Duke scientist have created the first map of this unique group of about 200 genes that may play an important role in an individual’s well being.
Normally when an individual is born, he/she inherits a copy of each gene from each parent and both copies are active, working in tandem with each other. But if one copy of the gene becomes mutated due to which it cannot work properly, the other copy compensates for its loss.
However imprinted genes or genetic imprinting destroys the backup of the the copy gene too. This means that a person may inherit an active copy of the gene only from one parent. Molecular signals imprint the other copy from the other parent to be silent.
As a result if one tumor suppressing gene is inherently silenced and the active one gets mutated the person becomes susceptible to cancer.
Silenced genes occur because sometimes, imprinting goes wrong before birth. A normally silenced gene becomes active and an active gene may become silenced. This faulty gene imprinting may lead to some devastating developmental disorders like Angelman Syndrome which causes mental retardation.
The Duke scientists have verified 40 such human imprinted genes and identified 156 more. Many of the newly found imprinted genes are in the regions of chromosomes which are already linked to development of obesity, cancer, diabetes and other diseases. Foe eg one may help to prevent bladder cancer and the other may be responsible for various types of cancer.
Behavioural and environmental factors also play a role here. They may reprogram the operation of some genes, by making them speed up or slow down or making the genes work at a wrong time. Factors like food, stress, pollution etc interact with the genes which determine why some people get sick, while others do not in the same situation.
To show how environment can re program some genes, pregnant mice were fed different nutrients to alter the coat colour of the babies. The feed affected the chemical signals that controls how hard a certain gene works, which determines if the babies had yellow coats like their mothers or brown ones.
According to the researchers it is not just about the sequence of the genes but how the sequence is affected by environmental exposures that determine whether a person will be healthy or not.
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