About 45 % of these familial melanomas have been attributed to inheritance of a mutation in a highly penetrant predisposition gene: CDKN2A (cyclin-dependent kinase 2 A) and less frequently in CDK4 (cyclin-dependent kinase 4), BAP1 (breast cancer associated protein-1), TERT (telomerase reverse transcriptase), and POT1 (protection of telomeres 1). The gene discussed is POT1; the disease is melanoma.