Dimples are considered mark of beauty and loveliness. The truth is that dimples are actually genetic defects that are caused by shortened facial muscles.
Dimples are caused by a fault in the subcutaneous connective tissue that develops in course of the embryonic development. A variation in the structure of the facial muscle may also cause dimples.
It must be interesting to note that dimples are inherited facial traits that are passed from one generation to the next. Dimples often occur on both the cheeks. A single dimple on one cheek is a rare phenomenon.
Transfer of dimples from parents to children occurs due to just one gene. The dimple creating genes are present in the sex cells prior to the process of reproduction. Each parent provides one of these genes to the child. So, if both the parents have dimples, the children have 50-100% chances of inheriting dimple genes.
If, however, only one parent has dimple genes, the chances of the children inheriting the genes are 50%. If neither of the parents has the dimple genes, their children will not have dimples.
As said earlier, dimples can be passed through multiple generations. The frequency with which a heritable trait is carried forth through genes is called penetrance.
Sometimes a variation in penetrance may also occur. Some individuals may carry a particular gene, but they do not manifest the traits associated with it. Nonetheless, they pass the traits to their successive generations.
Apart from that, sometimes the dimples may also be caused from spontaneous mutations that result in a dent in the cheek or a cleft chin that leads to dimples.
Apart from variable penetrance, there may also be reduced penetrance which allows a generation to skip having dimples, although they may appear in subsequent generations.
Reduced penetrance occurs when one person inherits certain genetic trait along with another trait that suppresses it. For example, a person may inherit genes for dimples and also other genes for small face. In this case the small face will not allow the gene for dimples to function. Such people are called passive carriers of dimple genes.
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