While the defective gene product in patients with PKU was identified using biochemical analysis, how ...

The cystic fibrosis gene was identified by a combination of genetic and modern molecular biology techniques. It was first localized to chromosome 7, and then molecularly cloned and sequenced. The sequence of the mutant allele was compared with the allele of a normal person to discover a three base-pair deletion in the cystic fibrosis gene. To determine the gene's function, its amino acid sequence and three-dimensional structure was deduced. This was compared with a database of protein sequences to determine the gene's function as an active transport protein.