Solving a Genetic Mystery

show/hide words to know

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.

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

 

 

 


References:

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

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

View Citation

You may need to edit author's name to meet the style formats, which are in most cases "Last name, First name."

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: December 10, 2018
  • Link: https://askabiologist.asu.edu/mendelian-traits-humans

APA Style

Dr. Biology. (2010, July 20). Human Traits. ASU - Ask A Biologist. Retrieved December 10, 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. 10 Dec 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.

Be Part of
Ask A Biologist

By volunteering, or simply sending us feedback on the site. Scientists, teachers, writers, illustrators, and translators are all important to the program. If you are interested in helping with the website we have a Volunteers page to get the process started.

Donate icon  Contribute

Share this page:

 

Share to Google Classroom