Allelic variation and linkage properties of a highly polymorphic restriction fragment in humans

The region between the human zeta-globin gene and the pseudo-zeta gene contains a stretch of tandemly reiterated 36 base-pair sequence elements. The structure of this locus offers the potential for unequal crossover events or slippage during replication to generate allelic variation in the length of restriction fragments spanning this region. The extent of allelic variation at this locus has been investigated in different populations at a high level of resolution. As many as ten discrete fragment lengths were observed whereas only three had been detected previously at a lower level of resolution. The linkage of alleles at this locus to closely flanking markers indicates that they are inherited as stable Mendelian traits over many generations, and therefore this and similar regions may provide highly polymorphic markers which will be of great value in genetic analysis of the human genome.