About K Shows Expertise I am able to answer questions regarding human medical genetics, mouse genetic studies, molecular biology, biochemistry, and cell biology. I am also able to answer questions concerning prenatal and postnatal genetic testing but am ethically unable to give advice on such test results.
Experience I have 10 years experience in human genetics, including clinical, population, and molecular genetics. I am currently an active researcher in molecular and developmental genetics at Virginia Commonwealth University/ Medical College of Virginia. I have previously taught genetics and cell biology at the college level.
Organizations American Association for the Advancement of Science (AAAS)
American Society of Human Genetics
Education/Credentials B.S., Biochemistry, University of Southern Mississippi
M.S., Human Genetics, Louisiana State University Medical Center
Ph.D., Genetics and Vision Science, University of Alabama at Birmingham
Thank you for this opportunity to ask a question. I am very much anticipating your response because I have found almost nothing on this subject and everything I have found is not complete or not make a lot of sense.So, again, thank you for this service.
I know so many people with facial dimples whose parents do not have facial dimples. I do not know how this is possible. Knowing that facial dimples is a dominant trait. For example, my sister in law has deep facial dimples and
only her great grandma had them in her family. So, is it because of variable penetrance, someone could be a carrier but does not show because of other factors? Or, perhaps it is a spontaneous mutation, knowing that dimples is a very minor defect? Professor, if you could give me some insight to this question, that would be great. Hope to hear from you..!
Nicole Wijedasa
Answer Nicole,
I think that the dimples trait is inherited as a tendency toward dimples, so that penetrance is not 100%. Cheek dimples occur when the muscles underneath the surface of the skin are shorter than the skin on top, so when you smile, the muscle pulls the skin at its attachment point, thus folding the top skin as it is pulled back. Chin dimples are actually a cleft chin in which the bones do not fuse completely (to form the face, the bony plates grow from the outsides to meet in the middle to form the mouth and lower part of the nose) and the outer skin lies on top of the cleft bone, revealing the structure underneath.
If you inherit the genes for dimples, that is, genes for short facial muscles or cleft chin, there may be other factors during your development that could lengthen the muscles, or allow full closure of the cleft chin. We know that several environmental factors can influence the growth of the face, as well as several different gene products that are only around during the facial development (the face develops during the first and second months of the life of the embryo, before many women know they are pregnant). In fact, sometimes dimples can be a marker for an underlying facial defect other than short muscles or cleft chin.
So, if dimples seem to skip generations in a family, it is probably due to reduced penetrance rather than new mutations. You are right: some people could be carriers and not show dimples because other factors "make up for" the short muscles or cleft chin that cause the dimples. For example, if a person has the gene for short facial muscles that cause cheek dimples but also inherits a gene for a small face, then the short muscles would then be proportional to the small face and then the dimples would not show.
