Origin of the chimeric p2/p1 gene by NHEJ.

The recombinant p2/p1 gene is represented as a rectangle above the filler DNA sequence shown in a yellow box. Exons 1 and 2 from p2/p1 are similar to p2, but the third exon is derived from P1-wr. The complex filler DNA (yellow rectangle) originated from two nearby downstream sequences as indicated by two gray balloons. A potential ancestral sequence, consisting of a putative p2 gene (tan rectangle) and a neighboring P1-wr gene (gray rectangle), is shown on top. DNA double-strand break, deletion and repair events resulting in the p2/p1 recombinant are explained in the main text.