Figure 1.

Insertion-deletion (indel) relative to the major allele as a function of GC content. For a total of 12 (10 rare alleles and 2 common alleles; for more details please see reference 7) indels, the partition of insertions (above the horizontal dashed line) and deletions (below the horizontal dashed line) into GC-rich and GC-poor minimal introns is almost absolute other than a single exception (red; the major allele is a deletion rather than an insertion). The rule that GC-rich and GC-poor minimal introns tend to have more insertions and more deletions, respectively, is by and large correct for human minimal introns [9].