One heavy chain variable region gene segment subfamily in the BALB/c mouse contains 500-1000 or more members

Nucleic acid hybridization studies suggest that 500-1000 or more heavy chain variable (VH) gene segments related to one VH gene segment (J558) are present in the genome of the BALB/c mouse. The implications of this result regarding the overall size, sequence organization, and evolution of the mouse family of VH gene segments are discussed.