A single gene can influence multiple phenotypic traits that are unrelated. This is known as pleiotropy. Pleiotropy occurs when a mutation in a single gene affects multiple physiological or anatomical traits. Examples provided in the document include Marfan syndrome, where a mutation in the FBN1 gene causes unrelated symptoms like tall stature, thin digits, eye lens dislocation and heart problems. Similarly, phenylketonuria results from a mutation affecting the enzyme phenylalanine hydroxylase, leading to both intellectual disability and reduced pigmentation. Sickle cell disease also demonstrates pleiotropy, as the beta-globin gene mutation causes sickle-shaped red blood cells and damage to multiple organs.

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:
1. Pleiotropy describes the genetic effect of a single gene on multiple
phenotypic traits.
2. Mutation in a pleiotropic gene may have an effect on some or all
traits.
3. 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:
I. Unsually tall height.
II. Thin fingers and toes.
III. 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

15. THANK YOU
When one gene influences multiple & unrelated phenotypic traits