Restriction Fragment Length Polymorphism

Fig. 1 Schematic representation of HLA class I and class II loci in the MHC that comprises >200 genes on the short arm of chromosome 6. The corresponding number of antigens (as defined by serology) and alleles (as defined by nucleotide sequence) is indicated for each locus. (From Ref. [1].) About 10% of the alleles assigned by the Nomenclature Committee are characterized by silent substitutions. Three HLA class I genes (A, B, and C) located at the telomeric end of the MHC encode, respectively, for the heavy chains of HLA-A, HLA-B, and HLA-C antigens that pair with b2-microglobulin. (From Ref. [2].) Polymorphic residues are essentially located in the a1-domains and a2-domains encoded by exons 2 and 3, respectively, which form the peptide-binding site. HLA class II antigens (DR, DQ, and DP) are heterodimers encoded by an a-chain and a b-chain gene that colocalize at the centromeric part of the MHC. Essentially all of the polymorphisms are located in exon 2 (a1-domain) of b-chain genes, whereas the DRA gene is non-polymorphic, and DQA1 and DPA1 loci exhibit a low level of polymorphism. The HLA-DR subregion presents an additional complexity level with the presence of a second DRB gene in most haplotypes: DRB3, DRB4, or DRB5. The nonclassical polymorphic HLA genes—HLA-DM, HLA-DO, HLA-E, HLA-F, HLA-G, 'MICA, and 'MICE—that code for molecules implicated in the immune response are also located in the MHC. (View this art in color at

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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