As shown in Fig. 4, the R1283G CFTR variant has negligible levels of chloride channel activity (ΔIsc = 0.7 ± 0.1 μA/cm2) which corresponds to less than 0.6% of WT CFTR function observed in Cystic Fibrosis Bronchial Epithelial (CFBE) cells. The gene discussed is CFTR; the disease is cystic fibrosis.