The minimal length of the differential segment in H-2 congenic lines.

One hundred and four H-2 congenic lines were typed for alleles at seven loci, Qa-1, Qa-2, Tla, C3, Ce-2, Pgk-2, and Upg-1, residing distal to the H-2 complex. The results of the typing were used to estimate the length of the segment of chromosome 17 derived from the donor strain of each line--that is, the minimal length of the differential segment. The results indicate that only lines derived by intra-H-2 crossing-over in such a way that they inherited the right-hand portion of H-2 from the inbred partner have the telomeric half of chromosome 17 identical with that of the inbred-partner strain. In other lines the differential segment is at least 3 to 10 cM long. It is argued that in some lines the entire telomeric half of chromosome 17 might be of donor-strain origin.