The BXD set of RI strains was developed in the laboratory of Benjamin Taylor and was transferred to The Jackson Laboratory from Dr. Taylor's research colony upon his retirement. Of 42 BXD RI strains originally derived from the C57BL/6J (Stock No. 000664) and DBA/2J (Stock No. 000671), a number have become extinct over the years. The other BXD RI strains now being distributed are listed under "Related Recombinant Inbred Strains."
In 1982/83 after BXD20/Ty (Stock No. 000330) had been intercrossed approximately 48 times (uncertain of exact date and filial generation number) one F20 BXD20/Ty male was outcrossed once to a single C57BL/6J female. The N1 offspring from this cross were then backcrossed to their sire, and this process was repeated 4 times. In total the outcross to C57BL/6J was followed by 4 consecutive backcrosses to the same F20 BXD2/Ty male. The line was then intercrossed and after 20 additional generations of inbreeding efforts began to cryopreserve the strain.
When BXD23/Ty reached F20 (year unknown) it is likely that a mouse was outcrossed and progeny backcrossed to the BXD23 mouse used for outcrossing, in a process similiar to the outcrossing done for BXD20/Ty (Stock No. 000330). However breeding records for BXD23/Ty are not available for generations prior to 1982 when the generation number is recorded as F20N5F34, presumably 34 filial generations later.
