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Human phenotypes that show Mendelian inheritance

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from Ask-A-Biologist

Below is a list of phenotypes easily identified in humans that follow the pattern of Mendelian inheritance. Look at yourself in the mirror to see if you carry the dominant or recessive alleles for these traits.

Mendelian Traits In Humans

Cleft chin (dominant) Chin without a cleft (recessive)

cleft chin

wikimedia – cutehappybrute

chin without cleft

wikimedia – david tribble
Cheek dimples (dominant) No cheek dimples (recessive)

Cheek dimples

wikimedia – c. szeto

no cheek dimples

ask a biologist – jacob mayfield
Free (dominant) earlobes Attached (recessive) earlobes

unattached earlobe

wikimedia – david benbennick

attached earlobe

wikimedia – covalent
Face freckles (dominant) No face freckles (recessive)

face freckles

wikimedia – loyna

no face freckles

wikimedia – david tribble
No Hitchhiker’s thumb (dominant)
Hitchhiker’s thumb (recessive)

hitckhiker's thumb

wikimedia – manic rage

normal thumb

wikimedia – drozd
Widow’s peak (dominant) No Widow’s peak (recessive)

widow's peak hairline

wikimedia – ccupload

flat hairline

wikimedia – ccupload

The expression of traits, however, is often far more complicated than in those listed above or those which Mendel observed in his garden. Sometimes tens, or even hundreds of genes can play a role in just one trait! In some cases, genes can block or exaggerate processes in the cell which change the visible phenotype. In other cases, environmental factors such temperature, light, and nutrient levels influence the development of a phenotype. Below is a list of traits in humans involving interaction between multiple genes.

Non Mendelian Traits in Humans

Eye color

black eyes

wikimedia – marc davis

brown/black eyes

wikimedia – pranav yaddanapudi

blue eyes

wikimedia – d. sharon pruitt


green eyes

wikimedia – pedram amiri


Hair Color

red hair

wikimedia – stephen key

black hair

wikimedia – marc davis

brown hair

wikimedia – alvesgaspar

blonde hair

wikimedia – nicolas genin
Ability to roll tongue

rolled tongue

wikimedia – gideon tsang

not rolled tongue



List of Mendelian traits in humans. In Wikipedia. Retrieved July 20, 2010, from http://en.wikipedia.org/wiki/List_of_Mendelian_traits_in_humans

Additional images via Wikimedia. Close up of iris by Petr Novák.





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