Core 1 beta 1,3-galactosyltransferases (core 1 GalTs) elongate O-linked N-acetylgalactosamine (O-GalNAc) by adding galactose in a β1,3 linkage, thereby building the 'T-antigen' or 'core-1' structure. In contrast to mammals, in which only one core 1 GalT has been identified, D. melanogaster has several such (putative) enzymes, each expressed in distinct patterns. (Adapted from
FBrf0207265.)