Pleiotrophism: Gene Interaction

Pleiotropy describes the genetic effect of a single gene on multiple phenotypic traits. 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.

1. PLEIOTROPISM Presented By Dr. Rajendra Chavhan Assistant Professor in Zoology Mahatma Gandhi Arts, Science and Late N. P. Commerce College Armori , District Gadchiroli Non- Mendelian Inheritance When one gene influences multiple & unrelated phenotypic traits

2. PLEIOTROPISM Non- Mendelian Inheritance Exception to Mendel’s Law When one gene influences multiple & unrelated phenotypic traits

3. The term pleiotropy comes from the Greek pleion meaning “more” and tropos , meaning “character” The term “Pleiotropic” was coined in a 1910 by ALAN BOND FESTSCHRIFT. PLEIOTROPISM History When one gene influences multiple & unrelated phenotypic traits Alan BOND FESTSCHRIFT

4. What is Pleiotropism ? When a single pair of gene control the production of many characters, then it is called PLEIOTROPISM. The gene is called PLEIOTROPIC gene. Definition: Pleiotropism is defined as when one gene influences multiple & unrelated phenotypic traits. PLEIOTROPISM When one gene influences multiple & unrelated phenotypic traits Pleiotropy  is the expression of multiple traits by a single gene.

5. PLEIOTROPISM General idea: Pleiotropy describes the genetic effect of a single gene on multiple phenotypic traits. Mutation in a pleiotropic gene may have an effect on some or all traits. Mechanism of pleiotropy in most cases is the effect of a gene on metabolic pathways that contribute to different phenotypes. Non- Mendelian Inheritance When one gene influences multiple & unrelated phenotypic traits

6. The term pleiotropy comes from the Greek pleion meaning “more” and tropos , meaning “character” . Pleiotropy was first noticed by geneticist  Gregor Mendel , who is known for his famous studies with pea plants. PLEIOTROPISM What Is Pleiotropy ? Pleiotropy  is the expression of multiple traits by a single gene. Gene pleiotropy  is focused on the number of traits and biochemical factors impacted by a gene. Developmental pleiotropy  is focused on mutations and their influence on multiple traits. Selectional pleiotropy  is focused on the number of separate fitness components affected by a gene mutation.  Antagonistic pleiotropy  is focused on the prevalence of gene mutations that have advantages early in life and disadvantages later in life. Expression of multiple traits by a single gene The ratio is 2:1 instead of 3:1.

7. PLEIOTROPISM Non- Mendelian Inheritance Example Example : Dobzhansky (1927) has demonstrated that When one gene influences multiple, unrelated phenotypic traits A gene for white eye in Drosophila , may affect the shape of sperm storage organs in females as well as other structure. White eye in Drossophila

8. PLEIOTROPISM Non- Mendelian Inheritance Example When one gene influences multiple, unrelated phenotypic traits Phenylketonuria  ( PKU) is an inherited disease in which the body cannot metabolize a protein called phenylalanine. The ratio is 2:1 instead of 3:1. Phenylketonuria, or PKU , is another disease resulting from pleiotropy PKU

9. PLEIOTROPISM Non- Mendelian Inheritance Example A classic example of pleiotropy is the human disease phenylketonuria (PKU). When one gene influences multiple & unrelated phenotypic traits This disease can cause mental retardation and reduced hair and skin pigmentation. Phenylketonuria is due to mutation in a single gene that codes for the enzyme Phenylalanine hydroxylase. Phenylalanine hydroxylase converts the amino acid phenylalanine to tyrosine, Due to mutation, conversion of phenylalanine to tyrosine is reduced or ceases entirely. PKU

10. PLEIOTROPISM Non- Mendelian Inheritance Example Phenylalanine in the bloodstream is toxic to the developing nervous system of new born and infant children and which causes mental retardation . When one gene influences multiple & unrelated phenotypic traits Where as tyrosine is used by the body to make melanine (an important component of the pigment found in hair and skin ). The failure to convert normal levels of phenylalanine to tyrosine results in less pigmentation of hair and skin. PKU

11. PLEIOTROPISM Non- Mendelian Inheritance Example For example, people with a hereditary disorder called Marfan Syndrome caused by the mutation in FBN1 gene may have a set of seemingly unrelated symptoms, including the following: Unsually tall height. Thin fingers and toes. Dislocation of the lens of the eye . IV. Heart problems (in which the aorta, the large blood vessel carrying blood away from the heart, bulges or ruptures). These symptoms don’t seem directly related. But as it turns out, they can all be traced back to the mutation of a single gene. This gene encodes a protein that assembles into chains, making elastic fibrils that give strength and flexibility to the body’s connective tissues start superscript, 4-end superscript, mutations that cause Marfan syndrome. When one gene influences multiple & unrelated phenotypic traits Marfan Syndrome

12. PLEIOTROPISM Non- Mendelian Inheritance Example When one gene influences multiple & unrelated phenotypic traits Humans is sickle cell disease. Sickle cell disorder Sickle cell is a result of a mutation in the beta-globin gene. This mutation results in red blood cells that are sickle-shaped, which causes them to clump together and become stuck in blood vessels, blocking normal blood flow. The single mutation of the beta-globin gene results in various health complications and causes damage to multiple organs including the  heart ,  brain , and  lungs . Human Sickle Cell Anaemia

13. PLEIOTROPISM Non- Mendelian Inheritance Example When one gene influences multiple & unrelated phenotypic traits Sickle cell disorder results from the development of abnormally shaped  red blood cells . Normal red blood cells have a biconcave, disc-like shape and contain enormous amounts of a protein called hemoglobin . The ratio is 2:1 instead of 3:1. Human Sickle Cell Anaemia

14. PLEIOTROPISM Non- Mendelian Inheritance Example When one gene influences multiple & unrelated phenotypic traits Frizzled Feather Traits

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