Interspecific Recombinant Congenic Strains
IRCS were derived by backcrossing 3 to 5 times Mus spretus mice
of the moderately inbred SEG/Pas inbred strains to C57BL/6J inbred strain.
About one first-generation backcross (BC1) male out of eight were fertile (18 out of 157). All of them were mated with B6 females. Their progeny were used to develop 4 to 8 strains. Each strain was maintained as 4 couples or trios. A total of 118 strains were initiated.
It is important to keep in mind that the initial cross was carried out in 1989, at a time when SEG/Pas was not inbred yet. Therefore, there might be some sequence differences between the Mus spretus alleles carried by one or the other IRCS and that present in the current SEG/Pas inbred mouse colony.
Interspecific Consomic Strains
ICS were derived by backcrossing at least 4 times Mus spretus
mice of the moderately inbred SEG/Pas inbred strains to C57BL/6J inbred strain.
Mice carrying the chromosome of interest were selected by microsatellite genotyping. The absence of Mus spretus alleles was checked using the same set of microsatellites. The majority of consomic strains were lost during the inbreeding process. The remaining six strains are presented here. For several chromosomes, particular regions could not be bred to homozygosity and hence were lost. Altogether, ICS complement IRCS and increase genome coverage.