Screening of all types of alleles of (A-C)n dinucleotide tandem repeat sequence of aldose reductase gene

The screening method of seven alleles (Z-6, Z-4, Z-2, Z, Z + 2, Z + 4 and Z + 6) in the (A-C)n dinucleotide tandem repeat sequence was studied. These alleles constitute a microsatellite DNA marker upstream of the transcription initiation site on the aldose reductase gene. At first, genoimic DNAs were isolated from leucocyte pellets, and the region containing the dinucleotide repeats was amplified by PCR with a pair of amplification primers that flanked 132-144 bp region. Then, the PCR products of the DNA samples whose alleles belonged to homozygotes were selected, purified, and sequenced directly in order to find out the types of alleles. Finally, using Z-2 allele as a marker, the samples containing Z-2 allele were detected by 12% fromamide-urea gel electrophoresis together with silver-staining. This method is simple, quick and accurate. It facilitates the screening of a large number of samples and is also suitable for identification of other dinucleotide tandem repeat sequences.