Solving a Genetic Mystery

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Gene: a region of DNA that instructs the cell on how to build protein(s). As a human, you usually get a set of instructions from your mom and another set from your dad... more

Inheritance: genetic information passed down from a parent.

Phenotype: the appearance of an individual that results from the interaction between their genetic makeup and the environment. Phenotypic trait... more

Trait: a characteristic of an organism that can be the result of genes and/or influenced by the environment. Traits can be physical like hair color or the shape and size of a plant leaf. Traits can also be behaviors such as nest building behavior in birds.

**Some of the content on this page is out of date, please pardon us while we update it for accuracy.**

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

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

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Bibliographic details:

  • Article: Human Traits
  • Author(s): Sabine Deviche
  • Publisher: Arizona State University School of Life Sciences Ask A Biologist
  • Site name: ASU - Ask A Biologist
  • Date published: July 20, 2010
  • Date accessed: May 21, 2024
  • Link:

APA Style

Sabine Deviche. (2010, July 20). Human Traits. ASU - Ask A Biologist. Retrieved May 21, 2024 from

American Psychological Association. For more info, see

Chicago Manual of Style

Sabine Deviche. "Human Traits". ASU - Ask A Biologist. 20 July, 2010.

MLA 2017 Style

Sabine Deviche. "Human Traits". ASU - Ask A Biologist. 20 Jul 2010. ASU - Ask A Biologist, Web. 21 May 2024.

Modern Language Association, 7th Ed. For more info, see
Close up showing a blue colored eye with hazel flecks

Eye color is not a Mendelian trait because it is controlled by several genes, in addition to other factors.

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