Starting from definition, pleiotropy is seen as a situation in which one gene controls for the expression of multiple phenotypic traits. These traits do not have to be clearly linked, i.e., eye color and eye shape, but can rather be completely unrelated. In many situations, this multi-trait impact is because of a gene code for a certain product, whereas that product/protein serves multiple roles in the body, catalyzes numerous interacts or reactions with various signal receptors. Pleiotropic impacts are most commonly noticed in conjunction with genetic disorders, since a mutation on a single gene may lead to multiple problems affecting development and growth, i.e., weight, height, skeletal development. If there had not been a mutation on that gene, the pleiotropic effect may have gone unnoticed. Some of the genetic disorders linked to pleiotropy include sickle cell anemia, Phenylketonuria, and Marfan Syndrome among others.

There are different types of pleiotropy, including gene pleiotropy, selectional pleiotropy, developmental pleiotropy, and antagonistic pleiotropy, all of which we are discuss in detail below.

Developmental Pleiotropy

This is the variation of pleiotropy that receives the most attention, as it is related to gene mutations and subsequent developmental disorders. This kinds of pleiotropy are when a mutation contains more than one effect on the resulting phenotype of the offspring.

Selectional Pleiotropy

The difference in this type and the one explained above is a little bit critical. While developmental pleiotropy can be related to a mutation on a gene that affects multiple phenotypic aspects, selectional pleiotropy is related to the different components of fitness that are affected by the mutation.

Selectional Pleiotropy Diagram

Gene Pleiotropy

Which can also be referred to as molecular-gene pleiotropy, this is a classification for genes related to the number of functions it has. These functions can be determined genetically, based on the number of traits affected by the gene, or biochemically, that is linked to the number of reactions a specific protein coded by the gene will catalyze.

Antagonistic Pleiotropy

This is seen as a fascinating form of pleiotropy, particularly because it affects everyone to a certain degree. In this case, a gene will have a beneficial impact on fitness at one point in an organism’s life, but a negative effect on fitness at a separate point in that organism’s life.

While some of mankind’s most feared diseases can be linked to pleiotropy, this is one of the unavoidable complexity of the human genome.



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