<prompt> What is the defect in Dubin Johnson syndromeMutation in ATP7B geneMutation in MRP - 2 geneMutation in UGT1A1 geneMutation in ATP7A gebe  <response>: In Dubin Johnson syndrome these is impaired biliary excretion of bilirubin glucuronides due to mutation in canalicular multidrug Resistance Protein -2 MRP- 2. 