by in situ hybridization on chromosome , phytohemagglutinin ( pha ) -stimulated lymphocytes obtained from normal individuals showed slight polymorphism in terms of distribution of rdna among nucleolar organizer region ( nor ) chromosomes probably due to racial differences , although their interindividual distinct polymorphism had been reported in the u.s.a .
C1518453
nucleolar organizer region
C0008633
chromosomes