This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: dermatology and infectious disease, Subject name: Pathology
Mutation seen in malignant melanoma is 
Select and explain. 
A. N-MYC, B. RB gene, C. CDKN2A, D. p53
C: CDKN2A
Answer: C: CDKN2A 
Explanation: CDKN2A is a complex locus that encodes three different tumor sup- pressors, p15/INK4b, p16/INK4a, and p14/ARF. Of these, loss of p16/INK4a is clearly implicated in human melanoma, and experimental evidence also suppos a role for loss of p14/ARF. As already mentioned, p16/ INK4a inhibits cyclin-dependent kinase 4 (CDK4) and cyclin-dependent kinase 6 (CDK6), thus reinforcing the ability of the RB tumor suppressor to block cells in the G1 phase of the cell cycle. By contrast, p14/ARF enhances the activity of the p53 tumor suppressor by inhibiting MDM2, an oncoprotein that stimulates p53 degradation. CDKN2A is mutated in approximately 10% of sporadic melanomas, and these mutations uniformly abolish the production of p16/INK4a and more variably affect p14/ ARF. However, it is suspected that these mutations are the tip of the "oncogenic iceberg" with respect to molec- ular lesions affecting the G1 checkpoint. For example, 30% to 70% of melanomas show loss of p16/INK4a expression though varied mechanisms, and other famil- ial and sporadic melanomas have mutations in CDK4