CFTR and cystic fibrosis: Typically, mice homozygous for a Cftr mutation or disrupted Cftr gene display many features common to a young person with CF caused by two severe mutations (ie p.Phe508del), including failure to thrive, meconium ileus, alteration of mucus and serous glands, and obstruction of gland-like structures with thickened eosinophilic material (Lavelle et al., 2016).