The stepwise addition of carbohydrate or carbohydrate derivative residues to the initially added O-linked residue (usually GalNAc) to form the core 2 O-glycan structure, GlcNAc-beta-(1->6)[Gal-beta-(1->3)]-GalNAc.
Source:
GOC:pr,
PMID:10580130,
GOC:mah