Solving a Genetic Mystery

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Gene: a region of DNA where a specific set of instructions for one trait is kept. We get some of our genes from our mother and some from our father... 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.

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

 

chin without cleft

Cheek dimples (dominant)

  No cheek dimples (recessive)

Cheek dimples

 

no cheek dimples

Free (dominant) earlobes   Attached (recessive) earlobes

unattached earlobe

 

attached earlobe

Face freckles (dominant)   No face freckles (recessive)

face freckles

 

no face freckles

No Hitchhiker's thumb (dominant)
  Hitchhiker's thumb (recessive)

hitckhiker's thumb

 

normal thumb

Widow's peak (dominant)   No Widow's peak (recessive)

widow's peak hairline

 

flat hairline

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

 

brown/black eyes

blue eyes

 

 

green eyes

 

Hair Color  

 

red hair

 

black hair

brown hair

 

blonde hair

Ability to roll tongue
 

 

rolled tongue

 

not rolled tongue

 


References:

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.

View Citation

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Bibliographic details:

  • Article: Human Traits
  • Author(s): Dr. Biology
  • Publisher: Arizona State University School of Life Sciences Ask A Biologist
  • Site name: ASU - Ask A Biologist
  • Date published: July 20, 2010
  • Date accessed: June 17, 2018
  • Link: https://askabiologist.asu.edu/mendelian-traits-humans

APA Style

Dr. Biology. (2010, July 20). Human Traits. ASU - Ask A Biologist. Retrieved June 17, 2018 from https://askabiologist.asu.edu/mendelian-traits-humans

American Psychological Association. For more info, see http://owl.english.purdue.edu/owl/resource/560/10/

Chicago Manual of Style

Dr. Biology. "Human Traits". ASU - Ask A Biologist. 20 July, 2010. https://askabiologist.asu.edu/mendelian-traits-humans

MLA 2017 Style

Dr. Biology. "Human Traits". ASU - Ask A Biologist. 20 Jul 2010. ASU - Ask A Biologist, Web. 17 Jun 2018. https://askabiologist.asu.edu/mendelian-traits-humans

Modern Language Association, 7th Ed. For more info, see http://owl.english.purdue.edu/owl/resource/747/08/
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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