A cleft or dimpled chin is an inherited trait, as explained by John H. McDonald of the University of Delaware. According to Genetic.com, this indentation is the result of a genetic defect that causes the right and the left side of the jawbone muscles not to fuse together properly during embryonic development. This gap is also present in the jawbone itself and causes the dimpled indentation to appear.
The cleft indentation in each person varies in size and shape. Several genes are responsible for the development of the cleft chin, including a modifier gene and the cleft gene. Even if both parents have cleft chins, their children may or may not have them. According to the University of Northern Iowa, the cleft gene is dominant to the smooth chin gene. Other factors, such as parental genotype, variable penetrance, environmental variables and modifier genes, affect the physical manifestation, or phenotype, of the final genotype, or genetic makeup, of a person’s chin.
The cleft in the chin does not cause any deformities or defects. Instead, it is simply a physical manifestation of a genetic trait. According to Wikipedia, some people who have lopsided jawbones can develop a cleft chin over time. Also, people who originate from Europe are more likely to have a cleft chin.