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What is Pleiotropy?
Pleiotropy, in genetics, is the expression of multiple traits using a single gene.
Pleiotropy comes from a Greek word that means more.
One simple example of Pleiotropy would be phenylketonuria, a form of disease. It is a genetic disorder that results in a low metabolism of the amino acids phenylalanine within the body cells.
Pleiotropy
Gregor Mendel, father of genetics, made many interesting observations about the colour of various plant components during his study on inheritance. Mendel observed that plants with coloured seed coats also had coloured leaf-axils, which connect leaves to stems. Mendel also observed that pea plants had colourless seed coats, with no pigmentation in their axils, and white-coloured blooms. The colour of the seed coating was determined by specific flower and axil colours.
We can now conclude that Mendel’s observations are based on pleiotropy, which is the phenomenon in which a single gene plays a role in multiple phenotypic characteristics. This shows that the gene responsible for seed coat colour wasn’t the only one. It also contributed to the axil pigmentation, and flower.
The mutation of the the FBN1 gene causes a human genetic disease, also known as the Marfan Syndrome. However, it can affect many aspects of growth and development, including height, vision, and heart function. These are all examples of pleiotropy, a gene that has multiple effects.
Gene Pleiotropy
Gene pleiotropy is a gene that focuses on the number and functions of a specific gene. It’s also known as molecular-gene pleiotropy.
We don’t think of phenotypes that are concerned with two colours when we discuss Mendel’s experiments using white-coloured flowers and purple-coloured plants. Mendel however observed that colours are always linked to two distinct features: the colour of the seed coat and the colour the axils.
Plants that bear white flowers have colourless seed coats and axils. Purple flowers have brown-grey seed coats and axils. The colour gene does not affect one trait, but three.
These genes control many unrelated features and are called pleiotropic. The term pleio means many and the term tropic means effects. This allows for the identification of distinct phenotypes back to a single gene that has different jobs.
The alleles for pleiotropic genes can be transferred in the same way that single traits are affected. A phenotype can have many elements. However, the elements are expressed in a package. The recessive or dominant versions of the package will be visible in the offspring from two heterozygotes at a ratio of 3:1.
Human Genetic Disorders
Most human genetic disorders affect genes that are pleiotropic. A person suffering from Marfan syndrome, a hereditary disorder, could experience a series of symptoms unrelated to the Marfan syndrome.
- Abnormal tall height
- Dislocation of the eye’s lens
- Toes and fingers that are lean
- Heart problems include ruptures of the aorta and large blood vessels which carry blood away from your heart
Although the symptoms above do not appear to be relevant, it is possible that it could be due to a mutation in a specific gene. This gene encodes a protein in chains, which makes fibrils that give strength and flexibility to connective tissue. Marfan syndrome is caused by a mutation that reduces the amount of functional proteins formed by the body, which results in fewer fibrils.
