Figure 2.

The shark β2M is linked to the MHC. A, The two-nucleotide (CC) deletion polymorphism was found in intron 2 of β2m sequences in “p3” paternal allele from siblings belonging to the groups “i” and “j.” Thus, allele-specific primers were designed based on this polymorphism. All primers are underlined. The ends of coding regions are boxed. The (AG) at the end of intron 2 is underlined. B, PCR was carried out with a combination of allelespecific and universal NSB2mEx3Rev reverse primers. Presence or absence of the amplicon using the “p3”-specific primers was used for typing (top gel) the family 2 with 39 offsprings. Maternal primers were used for the positive control (bottom gel). Forward primers are indicated on the left side of the gels, and mother and sibling numbers are indicated above the gel along with MHC groups (36). C, Allele-specific PCR in the families 1 and 3. Only two animals belonging to the MHC groups “h” possessed the “CC-deletion” allele, and two animals belonging to the “g” groups had this allele in family 3. We partially typed family 3 based on the MHC groups by sequencing of the PBR of the class Ia alleles (maternal and paternal alleles are designated as numbers above the gel) and by Southern blotting with a probe containing MHC class Ia leader and a1 domains (small dot, band for maternal haplotype 1; large dot, maternal haplotype 2). The “p2” allele of the “g” group is the only haplotype possessing the “CC-deletion” allele of β2M. D, Plot of LOD scores at corresponding recombination fractions. The sums of the two families were used (Supplemental Table I).