Is there a high rate of mitotic recombination between the loci encoding immunoglobulin VH and CH regions in gonial cells?

Rabbit sera from approximately 6000 offspring of matings informative for recombination at the immunoglobulin (Ig) heavy chain locus were tested with allotype antisera by double diffusion in gel. Seven recombinants were found, R1K-R7K, and in every case the recombinational event had taken place in the male parent. Two single males each fathered two recombinant offspring: R2K, R4K and R5K, R6K. Four further recombinants, reported from other laboratories as well as two new, as yet not fully documented recombinants in our laboratory, also occurred in the male parent. The recombinational events either separated the a locus which encodes the VH region of Ig, from the loci encoding its CH region or separated a-ms from the remaining linked loci d-e-f-g. The recombination frequency is 7/6142, approximately 0.1%. Our findings suggests that the recombinations took place in mitotic divisions during spermatogenesis. This work is the first evidence of gonial crossing-over in a mammal.