One gene, many phenotypes Prasun P, Pradhan M, Agarwal S - J Postgrad Med
Fjpg. Pleiotropic consequences of the HbS mutation in beta globin gene. Pleiotropy occurs when variation at a single gene locus affects multiple aspects. The pleiotropic effect is produced by a gene owing to a. both the mother and father must have and pass on the defective gene. The gene Hbs (recessive) is responsible for disease sickle cell anaemia. Here, gene 'Y' is recessive in relation to its effect on viability but dominant in relation to fur color. Nevertheless, at the phenotypic level, sickle cell anemia is not a monogenic In the last decade a number of epistatic genes and pleiotropic genes have been.
He recognized that "spurious" pleiotropy was present in the mutation, while "genuine" pleiotropy was not, thus partially invalidating his own original theory. In the mids Richard Goldschmidt and Ernst Hadorn, through separate individual research, reinforced the faultiness of "genuine" pleiotropy.
A few years later, Hadorn partitioned pleiotropy into a "mosaic" model which states that one locus directly affects two phenotypic traits and a "relational" model which is analogous to "spurious" pleiotropy. These terms are no longer in use but have contributed to the current understanding of pleiotropy. This mathematical model illustrates how evolutionary fitness depends on the independence of phenotypic variation from random changes that is, mutations.
It theorizes that an increasing phenotypic independence corresponds to a decrease in the likelihood that a given mutation will result in an increase in fitness. Genetic and Biometric Foundations by using molecular genetics to support the idea of "universal pleiotropy". The concepts of these various studies on evolution have seeded numerous other research projects relating to individual fitness.
Williams theorized that antagonistic effects will be exhibited during an organism's life cycle if it is closely linked and pleiotropic. Natural selection favors genes that are more beneficial prior to reproduction than after leading to an increase in reproductive success.
Pleiotropy: The concept, Phenylketonuria (PKU), Sickle cell anaemia
Knowing this, Williams argued that if only close linkage was present, then beneficial traits will occur both before and after reproduction due to natural selection. This, however, is not observed in nature, and thus antagonistic pleiotropy contributes to the slow deterioration with age senescence. The underlying mechanism is genes that code for a product that is either used by various cells or has a cascade-like signaling function that affects various targets.
Models for the origin[ edit ] One basic model of pleiotropy's origin describes a single gene locus to the expression of a certain trait. The locus affects the expressed trait only through changing the expression of other loci. Over time, that locus would affect two traits by interacting with a second locus. Directional selection for both traits during the same time period would increase the positive correlation between the traits, while selection on only one trait would decrease the positive correlation between the two traits.
Eventually, traits that underwent directional selection simultaneously were linked by a single gene, resulting in pleiotropy. Other more complex models compensate for some of the basic model's oversights, such as multiple traits or assumptions about how the loci affect the traits.
They also propose the idea that pleiotropy increases the phenotypic variation of both traits since a single mutation on a gene would have twice the effect. PKU is caused by a defect in the gene that helps create the enzyme needed to break down phenylalanine. Phenylketonuria is an autosomal recessive character controlled by a mutant gene present on the 12th chromosome.
An abnormal breakdown product phenylketone is found in urine. For a child to inherit PKU, both the mother and father must have and pass on the defective gene. This pattern of inheritance is called autosomal recessive. It also plays an important role in helping the body grow and develop properly. It is caused by a pleiotropic gene which is characterized by a slender body, limb elongation, hypermobility in joints, lens dislocation and tendency to develop heart diseases.
Marfan syndrome does not affect intelligence. Marfan syndrome is caused by a defect in the gene that enables your body to produce a protein that helps give connective tissue its elasticity and strength. Most people with Marfan syndrome inherit the abnormal gene from a parent who has the disorder.
Pleiotropy - Wikipedia
In these cases, a new mutation develops spontaneously. Normal or healthy gene is HbA.Pleiotropy
But can live a normal life. But the homozygotes with recessive gene Hbs die of fatal anaemia. Effect of the Pleiotropy in Mice: If there was no chromogen the mouse was albino.
Lethal gene in mice causes death at an early stage of development, often before birth. The effect of the lethal gene is illustrated by the inheritance of fur coat color in mice, In mice, yellow fur is dominant over non-yellow fur color.