MadSci Network: Genetics

Re: What does pleiotropic mean? What is the significance to cystic fybrosis?

Date: Thu Jul 13 10:58:06 2000
Posted By: Todd Wylie, Staff, Bioinformatics: Human Genome Project, Genome Sequencing Center: Washington University Medical School
Area of science: Genetics
ID: 959284748.Ge

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:

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).


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