|MadSci Network: Genetics|
Hi Joanna- Pleiotrophy is a scientific term regarding the ability of a single gene to simultaneously affect several phenotypic traits. A phenotypic trait is one that is visible or readily apparent upon examination (a genotypic trait is one on the molecular level that would require molecular analysis to define). For example - say that a gene mutates and causes it's carrier to ultimately have hair loss. In this case the genotype would be the genetic construction of the mutant gene and the phenotype caused by this gene would be visible hair loss. In pleiotrophic cases multiple phenotypes can be traced back to a particular gene. It helps to think of this in terms of cause and effect. The genetic defect underlying cystic fibrosis (CF) may cause multiple phenotypic traits depending on the severity of the disease in that person. Many organs can be affected (lungs, liver, pancreas, small intestine, reproductive tract, and skin) due to ducts or other pathways that become clogged with thick secretions or mucus that has not been properly dealt with by the body. Essentially, the lack of CFTR (a protein) causes improper regulation of the chloride channels in the body and chloride (Cl) is prevented from leaving the cells. This affects a wide range of organs in the body and hence there are multiple symptoms that can be exhibited. Keep in mind that the CF gene is not coding specifically for CF - rather it is a "normal" gene (that should produce a much needed protein) that has some of it's genetic code missing causing it to function improperly. There is a fantastic article on CF from Scientific American at the following site: http://www.people.virginia.edu/~rjh9u/cfsciam.html It has an extensive overview of the gene involving CF and discusses the other mutant variations on the most common DNA deletion mutation (which affects ~70% of CF patients). Regards, Todd
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