Cleft chin

Example of a cleft chin (William McKinley)

Human jaw front view

The terms cleft chin^[1], chin cleft^[2], butt chin^[1], superhero chin, dimple chin,^[3] or a chin dimple^[1] refer to a dimple on the chin. It is a Y-shaped fissure on the chin with an underlying bony peculiarity.^{[clarification needed][4]} The chin fissure follows the fissure in the lower jaw bone resulted from the incomplete fusion of the left and right halves of the jaw bone, or muscle, during the embryonal and fetal development. For other individuals it can develop over time, often because one half of the jaw is longer than the other, leading to facial asymmetry.^[1]

This is an inherited trait in humans, where the dominant gene causes the cleft chin while the recessive genotype presents without a cleft. However, it is also a classic example for variable penetrance^[5] with environmental factors or a modifier gene possibly affecting the phenotypical expression of the actual genotype.

See also

• List of Mendelian traits in humans

External Links

• Cleft Chin Genetics
• What Causes Cleft Chin?

References

1. ^ ^{a b c d} Mammalian Phenotype Browser:Cleft chin
2. ^ Sharks of the world, Vol. 2, pg. 143; by Leonard J. V. Compagno, Food and Agriculture Organization of the United Nations, 2001.
3. ^ Rob Roy, pg. 229 (in 1872 edition, pub. Osgood); by Sir Walter Scott, 1817.
4. ^ Online 'Mendelian Inheritance in Man' (OMIM) 119000
5. ^ Starr, Barry. "Ask a Geneticist". Understanding Genetics. TheTech. http://www.thetech.org/genetics/ask.php?id=47. Retrieved 2007-07-01.