Pleiotropy occurs when a single gene influences multiple phenotypic traits. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties A trait is a distinct phenotypic character of an organism that may be inherited environmentally determined or somewhere in between Consequently, a new mutation in the gene will have an effect on all traits simultaneously. In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism This can become a problem when selection on one trait favours one specific mutant, while the selection at the other trait favours another mutant. Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of

Contents 1 Etymology 2 Mechanism 3 Antagonistic pleiotropy 4 See also 5 References

Etymology

The term pleiotropy comes from the Greek pleio, meaning "many", and trepein, meaning "influencing". Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly A common mistake is to use "pleiotrophic" instead of "pleiotropic"

Mechanism

Pleiotropy describes the genetic effect of a single gene on multiple phenotypic traits. The underlying mechanism is that the gene codes for a product that is for example used by various cells, or has a signalling function on various targets.

A classic example of pleiotropy is the human disease PKU (phenylketonuria). Phenylketonuria ( PKU) is an Autosomal recessive Genetic disorder characterized by a deficiency in the enzyme Phenylalanine hydroxylase This disease can cause mental retardation and reduced hair and skin pigmentation, and can be caused by any of a large number of mutations in a single gene that codes for an enzyme (phenylalanine hydroxylase) that converts the amino acid phenylalanine to tyrosine, another amino acid. Mental retardation is a generalized triarchic disorder characterized by subaverage cognitive functioning and deficits in two or more adaptive behaviors with onset before the age Hair is a keratinised protein filament that grows through the epidermis from follicles deep within the Dermis. The skin is the outer covering of living tissue of an animal (or plant For the drug referred to as "pigment" see Black tar heroin. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Phenylalanine hydroxylase ( is an Enzyme which catalyses the reaction causing the addition of an Hydroxyl group to the end of the 6-carbon aromatic ring of In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this Phe redirects here For the BitTorrent feature see PHE. For the constellation see Phoenix (constellation. Tyrosine (abbreviated as Tyr or Y) or 4-hydroxyphenylalanine, is one of the 20 Amino acids that are used by cells to synthesize PKU is totally benign if a diet free from phenylalanine is maintained. Depending on the mutation involved, this results in reduced or zero conversion of phenylalanine to tyrosine, and phenylalanine concentrations increase to toxic levels, causing damage at several locations in the body.

Antagonistic pleiotropy

Antagonistic pleiotropy refers to the expression of a gene resulting in multiple competing effects, some beneficial but others detrimental to the organism. The antagonistic pleiotropy hypothesis was first proposed by George C Gene expression is the process by which inheritable information from a Gene, such as the DNA sequence, is made into a functional Gene product, such

This is central to a theory of aging first developed by G. C. Williams in 1957. Ageing or aging (American English is the accumulation of changes in an organism Professor George Christopher Williams (b May 12 1926 is an American Evolutionary biologist. ^[1] Williams suggested that some genes responsible for increased fitness in the younger, fertile organism contribute to decreased fitness later in life. One such example in male humans is the gene for the hormone testosterone. Testosterone is a Steroid hormone from the Androgen group In mammals testosterone is primarily secreted in the testes of males and the Ovaries In youth, testosterone has positive effects including reproductive fitness but, later in life, there are negative effects such as increased susceptibility to prostate cancer. Another example is the p53 gene which suppresses cancer, but also suppresses stem cells which replenish worn-out tissue^[2]. p53 (also known as protein 53 or tumor protein 53) is a Transcription factor encoded by the TP53 gene Stem cells are cells found in most if not all multi-cellular Organisms.

Whether or not pleiotropy is antagonistic may depend upon the environment; for instance, a bacterial gene that enhances glucose utilization efficiency at the expense of the ability to use other energy sources (such as lactose) has positive effects when there is plenty of glucose, but can be lethal if lactose is the only available food source. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology.

See also

• Epistasis
• Metabolic network
• Metabolic supermice
• Enhancer (genetics)

References

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