This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy of Skin, Subject name: Skin
Epidermal Melanin unit is? 
Select and explain. 
A. 26 keratinocytes : 1 melanocyte, B. 36 keratinocytes : 2 melanocytes, C. 16 keratinocytes : 1 melanocytes, D. 36 keratinocytes : 1 melanocyte
D: 36 keratinocytes : 1 melanocyte
Answer: D: 36 keratinocytes : 1 melanocyte 
Explanation: Ans. d. 36 keratinocytes: 1 melanocyteThe ratio of Epidermal-Melanin unit is 36 keratinocytes: 1 melanocyte.Each epidermal melanocyte together with the epidermal cells that it serves, comprises an 'epidermal melanin unit', as first described by Fitzpatrick and Breathnach in 1963. Although the number of active epidermal melanin units varies considerably in the different regions of the body, the number of keratinocytes served by each melanocyte remains constant. It is estimated that a single melanocyte supplies melanosomes to a group of about 36 viable keratinocytes.