Characterization of the β-spectrin mutations. Using the SSCP primers, and genomic DNA prepared from the patients' peripheral blood mononuclear cells, individual exons of interest were reamplified. The resulting DNA fragments were sequenced either by direct sequencing or by subcloning and sequencing of individual clones. Shown are the six frameshift and nonsense mutations of the β-spectrin gene. Note the base substitution in the cases of Sp Tabor and Sp Baltimore (nonsense mutations) reflected by the observation of two bands present at the same level by direct sequencing, as well as the base deletion or insertion (frameshift mutations) in the four other mutants seen by sequencing of individual clones.