The relationship between intron loss and processed pseudogene formation was not artifact. The 5th to 95th percentiles of the data are presented. (A) The mRNAs of parental genes of processed pseudogenes were significantly shorter than other genes (n = 637, median length = 1.434 kb versus n = 7,838, median length = 1.903 kb; Mann-Whitney U test, P < 10-16). (B) The mRNAs of intron-lost genes were slightly longer than no-intron-lost genes (n = 65, median length = 2.039 kb versus n = 8,410, median length = 1.860 kb; Mann-Whitney U test, P = 0.15). IL: intron-lost; NIL: no-intron-lost.