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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 resulting from the interaction between their genetic makeup and the environment. Phenotypic trait... more
- Trait: characteristics 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 birds building nests.
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)|
Cheek dimples (dominant)
|No cheek dimples (recessive)|
|Free (dominant) earlobes||Attached (recessive) earlobes|
|Face freckles (dominant)||No face freckles (recessive)|
|No Hitchhiker's thumb (dominant)||Hitchhiker's thumb (recessive)|
|Widow's peak (dominant)||No Widow's peak (recessive)|
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, environment 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
|Ability to roll 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.