Detection of microsatellites by ethidium bromide staining. The analysis of an STR system in the human phenylalanine hydroxylase gene.

The analysis of short tandem repeat (STR) systems usually relies on polyacrylamide gel electrophoresis analysis followed by visualization with silver staining or autoradiography. Both these techniques may not be suitable for clinical laboratories. We developed a simple procedure based on the visualization of STR alleles by ethidium bromide staining. The 4-bp STR system analysed is located in the human phenylalanine hydroxylase gene. Alleles differing by 4 bp are clearly separated independently of the size of the amplified fragments and homozygous samples are easily identified by comparison of the relative intensity of the electrophoretic bands. This method could be applied to the analysis of other STR systems located in different genetic loci by carefully changing the electrophoretic conditions.