Alleles control sites

Thus the direction of polarity in the operon and the observed differences between strains containing deletions of the type B.. Cleu and 5.. C on the one hand and Cleu on the other, with regard to sensitivity to activation by L-arabinose (C allele in the trans position), offer conclusive proof that the activator-sensitive controlling site aral) is located between genes araB and araC. 

How is it possible for these two deletions to bring about such different modifications of the effect of the allele No doubt the answer lies in the fact that the left end of deletion 766 terminates within the C gene, while the left end of deletion 719 terminates somewhere in the region between araB and araC, which, as we have shown, harbors at least one of the controlling sites for this operon. These results become meaningful if we assume that (1) deletion 719 extends into the area of the controlling site and excises an operator region which we propose exists between aral and araC, and (2) the product formed by the C" allele in the absence of L-arabinose is a repressor (PI) in equilibrium... 

The original application of the haplotype method was to allele frequency data (99). Direct roles of only HLA DR3 and DR4 serological types in type-1 diabetes were excluded, since HLA B locus variation on these haplotypes was different in patients and controls. At the amino acid level, a combination of sites at DRB1, DQA1, and DQB1 was shown to be highly correlated with the DR-DQ contribution to type-1 diabetes and to correlate with disease incidence (101). 

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