On GATAGATA and other "junk" in the barren stretch of genomic desert.

(GATA)n and additional simple repeated DNA sequences have long been known but functional analyses along traditional research strategies have not yielded definitive results. Therefore these elements are commonly regarded as genomic "junk" although they represent assets for innovative methodological approaches and especially for speculations. While extensively using microsatellites for genome mapping and genetic relationship analyses, it was also realized that certain simple repeats can cause human trinucleotide block expansion diseases. Hence these simple repeat elements comprise an exceptional range of biological meaning, i.e. from genetically absolutely neutral markers for genome analysis, behavioral and population genetic studies to dominant and invariably disease causing mutations with complete penetrance. The quest into why there is so much repetitive junk in recent genomes can be answered only in part and sequentially, but sometimes--even after substantial efforts--not for the given element.