To explain the unusual mass of the detected fragment one should consider two factors: (i) MUC1 displays much higher level of glycosylation in normal cells compared to cancer cells, which has a strong effect on its electrophoretic mobility, and (ii) there are many splicing isoforms of MUC1, including those where (due to the disruption or deletion of the SEA domain) MUC1 consists of one long chain26. The gene discussed is MUC1; the disease is cancer.