chem ical ▁and ▁imm un ological ▁properties ▁with ▁other ▁m amm al ian ▁lines , ▁especially ▁p ig ▁skin . ▁P ig ▁skin ▁shares ▁similar ▁e pid erm al ▁and ▁der mal ▁thick ness ▁r ati os ▁to ▁human ▁skin ; ▁p ig ▁and ▁human ▁skin ▁share ▁similar ▁hair ▁fol lic le ▁and ▁blood ▁vessel ▁patterns ; ▁bio chem ically ▁the ▁der mal ▁col lagen ▁and ▁el astic ▁content ▁is ▁similar ▁in ▁p ig ▁and ▁human ▁skin ; ▁and ▁p ig ▁skin ▁and ▁human ▁skin ▁have ▁similar ▁physical ▁responses ▁to ▁various ▁growth ▁factors . ▁ ▁Sk in ▁has ▁mes od erm al ▁cells , ▁p ig ment ation , ▁such ▁as ▁mel an in ▁provided ▁by ▁mel an ocy tes , ▁which ▁abs orb ▁some ▁of ▁the ▁potentially ▁dangerous ▁ult rav io let ▁radiation ▁( U V ) ▁in ▁sun light . ▁It ▁also ▁contains ▁DNA ▁repair ▁en zym es ▁that ▁help ▁reverse ▁U V ▁damage , ▁such ▁that ▁people ▁lack ing ▁the ▁gen es ▁for ▁these ▁en zym es ▁suffer ▁high ▁rates ▁of ▁skin ▁cancer . ▁One ▁form ▁pre domin antly ▁produced ▁by ▁U V ▁light , ▁m align ant ▁mel an oma , ▁is ▁particularly ▁invas ive , ▁causing ▁it ▁to ▁spread ▁quickly , ▁and ▁can ▁often ▁be ▁dead ly . ▁Human ▁skin ▁p ig ment ation ▁var ies ▁among ▁populations ▁in ▁a ▁striking ▁manner . ▁This ▁has ▁led ▁to ▁the ▁classification ▁of ▁people ( s ) ▁on ▁the ▁basis ▁of ▁skin ▁color . ▁ ▁In ▁terms ▁of ▁surface ▁area ,