Pleiotropism: what is it and how it affects the characteristics of people

Science is advancing and the knowledge of genetics and heredity is becoming more and more precise, allowing new discoveries to be revealed in the human genome. For its part, genetics studies genes and how we inherited the traits that our parents pass on to us.

In this article we will see what pleiotropism is, A phenomenon whereby a single gene affects several phenotypic traits in the same organism, usually unrelated to each other. We will know the differences between genotype and phenotype, and some examples of pleiotropism.

    Pleiotropism: what is it?

    The word pleiotropism comes from the Greek “pleion”, which means more, and “tropos”, which means change; the terms polyphenia or multiple phenotypic expression are also used, but less.

    Pleiotropism appears when a single gene affects more than one phenotypeThat is, in addition to a phenotypic characteristic (e.g. eye color, hair color, height, freckles, etc.)

    When genetics began to be studied, already in the days of Mendel’s laws, it was initially believed that every trait or trait was controlled by a single gene. They later discovered that there were cases in which the manifestation of a trait might require the participation of more than one gene, and on the contrary, that the same gene could determine several characteristics (pleiotropy).

    the story

    The word “pleiotropy” it was first used by a German geneticist, Ludwig Plate, 1910.

    Plate used the term to explain the appearance of several different phenotypic traits that always occur together and may appear to be correlated. According to him, the fact that this happened was due to a unit of pleiotropic inheritance.

    Genetics and human heritage

    Pleiotropism is a concept inherent in the genetics of development. Genetics is the part of biology that studies the genes and the mechanisms that regulate the transmission of inherited traits. And, more specifically, developmental genetics is the part of genetics that specializes in characterizing the causes by which organisms develop in a particular way.

    Genetic inheritance is the process by which characteristics of individuals are passed on to their offspring. These characteristics are physiological, morphological and biochemical.

    On the other hand, the concept of pleiotropism encompasses two other terms: genotype and phenotype.

    1. Genotype

    It is the set of invisible characteristics that a living being inherits from its parents. In other words, it would be the set of all the genes he inherits; genes contain the genetic information (or material) of the individual.

    2. Phenotype

    These are the “visible” characteristics that the person inherits from his parents, that is to say the set of traits of an individual. For example, skin color, height, shape of ears, facial features, etc. The phenotype results from the interaction between a person’s genotype and his environment.

    The phenotype includes not only physical traits, but also behavioral traits (eg, impulsivity, patience, temperament, etc.).

    3. Differences between the two

    like that, the difference between genotype and phenotype is that the genotype can be distinguished by observing DNA, and the phenotype is known by observing the external appearance of an organism.

    How does pleiotropy occur?

    The mechanism by which pleiotropism occurs is that the same gene is activated in different tissues, producing different effects; this is a very common occurrence, as most genes affect more than one tissue.

    Examples of diseases caused by pleiotropism

    As we have seen, pleiotropism is the condition in which the mutation in a single gene affects multiple phenotypic characteristics in the same organism. Often these pleiotropic effects or phenotypic characteristics are not relatedIn other words, they are independent.

    Some examples of pleiotropism in humans are sickle cell anemia, Marfan syndrome, and Holt-Oram syndrome.

    1. Sickle cell anemia

    Sickle cell anemia occurs by pleiotropism, and it’s a hereditary disease which affects hemoglobin, a protein that is part of red blood cells and is responsible for transporting oxygen. In this case, the body produces abnormally shaped red blood cells (sickle).

    Sickle cell anemia is the product of a genetic disease; people with the disease are born with two sickle cell genes, one from each parent. The presence of the sickle cell gene and a normal gene is called a sickle cell trait.

    2. Marfan syndrome

    Marfan syndrome, also a case of pleiotropism, is a disease that affects connective tissue. A series of skeletal, eye and cardiovascular abnormalities occur in the body, Which have as a common basis a defect of connective tissue fibrillin.

    all these symptoms are directly related to the mutation of a single gene, The FBN1 gene, which is pleiotropic. The function of this gene is to encode a glycoprotein which is used in the connective tissues of different parts of the body.

    3. Holt-Oram syndrome

    People with this syndrome have an abnormality of the carpal bones and other bones of the forelimbs. In addition, about 3 in 4 patients with Holt-Oram syndrome also have heart problems.

    Bibliographical references:

    • Brooker, RJ (2017). Genetics: analysis and principles. McGraw-Hill Higher Education, New York, New York, USA.
    • Lobo, I. (2008). Pleiotropy: one gene can affect multiple traits. Nature education, 1-10.
    • Nitxin, A., Araneda, C., Pascual, L., Barbadilla, A. and Carballo, MA (2010). Extensions to Mendelian principles: pleiotropy.
    • Sánchez Elvira Paniagua, A. (2005). Introduction to the study of individual differences. Madrid: Ed. Sanz and Torres. 2nd edition.

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