Genetic Influences

Polymorphisms
Polymorphisms are normal genetic variances seen in the general population. They do not alone provide for a medical condition or disorder. However, polymorphisms of certain genes are often seen with more frequency in disorders, such as obesity, hypertension and diabetes. Not every person who has a polymorphism associated with a disorder gets the disorder. This suggests that there are other factors involved in determining the onset of a disease or disorder, factors which we believe to be environmental. The significance of having a polymorphism may also depend on which cell component is involved.

In the case of a polymorphism in a cell receptor or a growth factor, the fetal environment could be a determining factor in whether a disease or disorder develops. Polymorphisms that occur in cell receptors may provide increased or decreased susceptibility to environmental factors by being more or less active in their functioning. This may then have an affect on the critically-timed cell signaling that determines how we develop in the womb. For this reason we believe genetic factors, such as polymorphisms in genes for cell receptors and growth factors, may influence fetal physiology and eventual human functioning.

The Beta2 Adrenergic Receptor is an example of a cell surface receptor, which has polymorphisms and provides a model for genetic vulnerability that may be acted on by environmental factors.

A recent finding in the gene for the cell receptor called MET may provide another example of genetic vulnerability to environmental factors. The MET cell receptor, which is stimulated by certain growth factors, is known to be involved in brain development, regulation of the immune system and repair of the gastrointestinal tract. A recent study indicates that having a variation in the gene for the MET cell receptor increases the risk of autism. Having the variation in the gene does not directly cause autism but increases the chance of having the disorder. It is believed that environmental factors are also involved but they have not yet been identified.

It is clear that further research is needed to determine the significance of genetic variances that create vulnerability to environmental factors.