CDKN2A and melanoma: In conclusion, although approximately 50% of melanoma-prone families display linkage to 9p21, only about half of these have been identified as carriers of mutations in the CDKN2A gene by direct exon sequencing (Hussussian et al, 1994; Kamb et al, 1994; Harland et al, 1997; Borg et al, 2000).