Fig 1.

Variation in MHC class II promoters of inbred wild-derived mice, n = 23–24. Nucleotide position is counted backward from the start of transcription (A in ATG = 0). Polymorphisms are labeled thus: * denotes those found to be in linkage disequilibrium (see Fig. 2); ○ denotes one not in linkage disequilibrium with the others marked. The transcription factor binding sites S, X1, CRE, and rCAAT as labeled (Middle) and have similar locations in Top and Bottom. The CRE zone extends through 10 bases flanking CRE on either side, as explained in the text. The axis label % frequency of rare allele(s) indicates the total frequency of all bases other than that of the most common allele at the position shown. The axes are scaled similarly.