The classical genetic approach to finding the gene that is responsible for causing a genetic disease has been to first characterize the bio-chemical defect within the gene, then to identify the mutated protein in the gene of interest, and finally to locate the actual gene. However, this classical approach proved to be impractical when searching for the CF gene. To find

An Account of the Absorption and Secretion of Cl-, Na+, and Proteins

Chloride conductance channels have dramatic potentials. One channel can conduct from 1x106 to 1x108 ions per second.8 This is particularly impressive when you consider the fact that there are not any channels present on cells to perform the required tasks. As a result of this, a mutation of one channel or even a partial mutation of a channel, that causes a decrease in the percentage of channel openings, can exert a major effect. Even the mildest of cures altering the Cystic Fibrosis Conductance Regulator in CF afflicted people would lead to significant improvements in that individuals health. Since cystic fibrosis is the most common genetic disorder, particularly amongst Caucasians, in today's society, intense research efforts towards its cure would be invaluable. When will cystic fibrosis be completely cured? No one can say for sure but, strong steps have already been taken towards reaching this goal.

An inward, electrochemical Na+ gradient is generated by the Na+, K+-ATPase pump located in the basolateral membrane (the cell side facing the organ it is lining). A basolateral co-transporter then uses the Na+ gradient to transport Cl- into the cell against its own gradient. This is done in such a way that when the apical Cl-channels within the membrane spanning domain open, Cl- diffuse passively with their gradient through the cell membrane.4 In pancreatic duct cells, a Na+, H+-ATPase pump is used and a bicarbonate secretion is exchanged for Cl- uptake in the apical membrane. Chloride ions then diffuse passively when the Cl- channels are opened. Such secretions also allow for the exocytosis of proteins in the pancreas which will later be taken into the small intestines for the breaking down of carbohydrates.4 In addition to the pump-driven gradients and secretions, there exists autonomic neurotransmitter secretions from epithelial cells and exocrine glands. Fluid secretion, including Cl-, is stimulated predominately by cholinergic, a-adrenergic mechanisms, and the b-adrenergic actions.4 Such chemical messengers cannot enter the cell, they can only bind to specific receptors on the cell surface and transmit messages to and through an intracellular messenger such as Ca2+ and cAMP by increasing their concentration. The intracellular message is transmitted across the cell by either diffusion or by a direct cascade. One example of a directed cascade is the following:

The isolated gene was proven to be responsible for causing CF by comparing its base pair sequence to the base pair sequence of the same sequence in a non-affected cell. The entire CF cDNA sequence is approximately 6,000 nucleotides long. In those 6,000 n.t.'s, three base pairs were found to be missing in affected cells, all three were in exon #10. This deletion results in the loss of a phenylalanine residue and it accounts for seventy percent of the CF mutations. In addition to this three base pair deletion pattern, up to 200 different mutations have been discovered in the gene accounting for CF, all to varying degrees.

Some common words found in the essay are:
CF RNA, ATP UTP, Defect Studies, Na+ H+-ATPase, Mutations NBF, Fibrosis Gene, Caucasians Cystic, Cystic Fibrosis, Francis Collins, Conclusion Chloride, cystic fibrosis, cf gene, cell types, base pairs, membrane spanning domain, blot electrophoresis, membrane spanning, spanning domain, fibrosis gene, conductance regulator, sweat glands, cystic fibrosis gene, base pair sequence, fibrosis transmembrane conductance, southern blot electrophoresis,
Approximate Word count = 2158
Approximate Pages = 9 (250 words per page double spaced)