Nature of the mutation

The b692 allele has a single T-to-G point mutation that replaces isoleucine with serine at position 215 of the helix-loop-helix dimerization domain’s first helix (Lister et al.,Developmental Biology 237: 333-344, 2001).

Genotyping assay

The RFLP (Restriction Fragment Length Polymorphism) assay is used to genotype the b692 allele.Botstein et al., Am. J. Hum. Genet. 32: 314-331, 1980; polymorphism). This method is used to detect a mutation that adds or removes a site recognised by a specific restriction enzyme. In the RFLP assay, a sequence of interest is PCR-amplified first, and then the PCR is stopped.The product is digested with restriction enzymes. The presence or absence of the mutation is determined.The resulting restriction pattern determines The b692 mutation results in the formation of a site that is recognised by BsrDI is a restriction enzyme.