Physical assignment of the bovine MHC class IIa and class IIb genes

Screening of a bovine yeast artificial chromosome (YAC) library revealed tw o clones which contain most of the class II genes of the major histocompati bility complex (MKC) known to date. The YACs were mapped by fluorescence in situ hybridization (FISH) and characterized for the class II genes they co ntain. We found that the classic class II genes BoLA- DQA, -DQB, -DRA, and -DRB3 are located at BTA 23q21 and the non-classic class II genes DYA DIB, LMP2, LMP7, TAP2, BoLA-DOB, -DMA, -DMB, and -DNA are located at BTA 23q12-- >q13. These two different mapping locations confirm and extend previous fin dings of a gross physical distance between classic and non-classic MHC clas s II genes in cattle.