Schematic figure of the genomic focus region of the MHC. Genes are illustrated by white arrows indicating their orientation, with the names above the drawing. The exon-intron structure is given for BLB1 and BLB2 to show the target region and primer positions. The positions and amplification directions of all primers used in this study are indicated by small one-headed arrows. Below the upper part of the drawing, the primers for the long-range PCR amplifications of BLB1 and BLB2 (C275, NBG262 and preBLB2F, BLBex3R) are given. Further down, the target region Exon 2 is enlarged, with the positions of the nested PCR primers (BLB1: RNAR1a, RNAF1a, NBG262; BLB2: Vorinex, RNAF1a, RNAR1a, Postex) given below. Note that BLB1 and BLB2 are orientated in opposite directions.