Introduction: Current investigations and theories on the genetic defect in cystic fibrosis.

Recent research in cystic fibrosis has suggested at least two theories regarding 
the genetic defect underlying this prevalent disease: that a mutant gene 
in cystic fibrosis genotypes is responsible for the synthesis of an 
altered protein that interferes with membrane transport and mucociliary activity; and 
that a mutant gene in cystic fibrosis genotypes is responsible for 
an enzyme deficiency leading to the presence of undegraded metabolites that 
interfere with membrane transport. Circulating factors in cystic fibrosis and their 
effects on membrane transport and mucociliary systems are discussed, as are 
the search for an enzymatic deficiency and investigations of altered metabolic 
pathways. Comparison of somatic cells from cystic fibrosis and normal genotypes 
is also outlined. 