In general, one gene controls one particular character. Pleiotropic gene is different from other gene, as it shows effects to more than one character. In other words, one gene that performs many effects over the other in the body of organism. The gene which has the ability to control more than one character is the pleiotropic gene. This can refer from various mechanism like overlapping, selective, genetic and so on. When a gene combines or catalyze with many other catalyzing gene or proteins. Also, In development, pleiotropy occurs during the development of gene by mutation. In selection pleiotropy, the change occurs due to many phenotypes, which is depending on age and gender.
Let's see an example of pleiotropy, phenylketonuria, which is not a hereditary disorder. This type affects the phenylalanine level in which is obtained by amino acids. We all know that, if more number of ATP is not good sign. It may cause severe and dangerous effects. Sometimes pleiotropy also affects nervous system too. The disease or disorder can affect various system of a body. Moreover, pleiotropy not only affects human, also animals like mice, chickens. The pleiotropic genes may result in limitations in the rate of multivariate. Even in the natural and intercoursing selection. Also, some alleles are very dangerous as well as harmful to the body of organism. Mostly, Correlation and the response given to selection affects pleiotropy.
Pleiotropy is a disorder where multiple and different organ system are affected by a gene. And there is a lot of difference between polygenic and pleiotropy. Polygenic is an inheritance which is inherited or influenced by independent gene. They may have similar and same effect in the body. But pleiotropy is a gene that controls various system. A single gene controls different and multiple traits in the body.
Sometimes, this disorder correlates with environment. If the fitness of alleles adopts to environment, then it can be considered as environment pleiotropy. In the Same way, if the disorder helps in a useful manner or the effects by the disorder is gain for an individual, then it may be a positive pleiotropy.
Sickle cell anemia is an example of pleiotropy. Here, pleiotropy is an Autosomal recessive disorder. This recessive disorder is due to point mutation. The normal polypeptide is made up of amino acid, the combined amino acids are, valine, Leucine, treeline, proline, glutamic acid etc. In sickle cell anemia, when point mutation takes place, the glutamic acid replaced. The mutation only happens in one place, so the glutamic acid replaced by valine. This is actually called as sickle cell anemia.
Basically, in sickle cell anemia, the change in sixth place as in beta chain. And glutamic acid replaced with valine. Which is the cause of sickle cell anemia. This example is for understanding.
The change may be in different variety like shape, molecules, size etc... When a gene has ability to control more than two traits, called pleiotropy.
Conclusions:
The simple words for remembering the pleiotropy is, the ability of a gene to control more two traits. This may result in both positive manner and in negative which is very harmful to the body of organism which affects different systems
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