Cheek dimples when present, show up when a person makes a facial expression. A chin dimple is a small line on your chin that stays on your chin without making any facial expressions. Dimples may appear and disappear over an extended period. Professor McDonald, citing limited research, concludes dimples have been mislabeled as genetically inherited and as a dominant trait. However, the University of Utah considers dimples an "irregular" dominant trait that is probably controlled mostly by one gene but is influenced by other genes.
Dimples are a facial muscle deformity. Dimples may be caused by variations in the structure of the facial muscle known as zygomaticus major. Specifically, the presence of a double or bifid zygomaticus major muscle may explain the formation of cheek dimples. This bifid variation of the muscle originates as a single structure from the zygomatic bone. As it travels anteriorly, it then divides with a superior bundle that inserts in the typical position above the corner of the mouth. An inferior bundle inserts below the corner of the mouth.
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- Pessa, JE; Zadoo, VP; Garza, PA; Adrian Jr, EK; Dewitt, AI; Garza, JR (1998). "Double or bifid zygomaticus major muscle: anatomy, incidence, and clinical correlation". Clinical Anatomy 11 (5): 310–3. doi:10.1002/(SICI)1098-2353(1998)11:5<310::AID-CA3>3.0.CO;2-T. PMID 9725574.
- McDonald, J.H. "Myths of Human Genetics". Sparky House Publishing. Retrieved 10 January 2015.
- Utah. "Observable Human Characteristics". Retrieved 26 January 2015.
- "Dimple Creation – Cute as a button, who pays for a deformity?".
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