x1 = MrnaP21
x2 = MrnaCy
x3 = MrnaP53
x4 = P21
x5 = Cy
x6 = CyP21
x7 = aPcna
x8 = Rc
x9 = pRc
x10 = aRc
x11 = iRc
x12 = Dna
x13 = Dam
x14 = P53
x15 = Skp2
x16 = Cdt2
x17 = iPcna
x18 = tP21
x19 = tCy
x20 = tPcna