The lengthening or shortening of the non-coding regions of specific genes during their evolution. A pairwise alignment of about 6,000 orthologous genes demonstrates that the equivalent introns in genes of Drosophila are only half the length of Anopheles introns, whereas the exon lengths and intron frequencies are similar in both insects. Therefore a change in intron lengths has occurred during the period since the divergence of fruit flies and mosquitoes from a common dipteran ancestor (about 250 million years ago). This difference in intron lengths explains why the A. gambiae genome is larger than the D. melanogaster genome (278 vs 180 mbp), although both species have 13,000–14,000 genes. See Chronology, 2002, Holt et al.
Subjects: Genetics and Genomics.