molecular typing detects DNA sequence variation, and
distinguishes 8 DQA1 and 16 DQB1 alleles. The differences
in the sequence reflects changes in structure of the cleft
of the DQ molecule, which is critical for the presentation
of antigens. DQA1 alleles coding for an arginine in position
52 (i.e., DQA1*R) and DQB1 alleles coding for an amino acid
other than aspartic acid in position 57 (i.e., DQB1*ND) are
significantly more common among type 1 diabetics than controls.
These haplotypes represent the best single genetic marker for
molecular epidemiology studies of type 1 diabetes.