The human immunoglobulin heavy chain transgene in the foregoing animals comprises {HEAD ~ a human constant region gene segment} comprising {TAIL ~ exons} encoding the desired heavy chain isotype, operably linked to switch segments from a constant region of a different heavy chain isotype, i.e., a non cognate switch region 
The human immunoglobulin heavy chain transgene in the foregoing animals comprises { HEAD ~ a human constant region gene segment } comprising { TAIL ~ exons } encoding the desired heavy chain isotype , operably linked to switch segments from a constant region of a different heavy chain isotype , i.e. , a non cognate switch region
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH