Occult microhomology G/C content fingerprint in FLT3-ITD junctions. (A) Percentage G/C content of the 20-nt positions flanking the FLT3-ITD repeat junction derived from 226 duplication junctions (N-nucleotide filler, n = 97; no visible microhomology, n = 70; 1 bp of microhomology, n = 59). Junctions with ≥2-bp microhomology were excluded, as their visible germline homology may be considered sufficient to prime MMRDR, and only a limited number of reintegration sites are available. A significant G/C spike is visible at position +1 (red). (B) Junction G/C content for individual junction categories. Error bars show standard error of the mean. There is no increase in G/C content for junctions with ≥2-bp microhomology (n = 49). MH, microhomology.