| Comments |
P.1312 left column bottom paragraph: "[Investigators] compared the average size of genomic elements of birds with 24 mammalian and the three nonavian reptile genomes. Avian protein-coding genes were on average 50 and 27% shorter than the mammalian and reptilian genes, respectively (Fig. 2A). This reduction is largely due to the shortening of introns and reduced intergenic distances that resulted in an increased gene density (Fig. 2A). Such genomic contraction has also evolved convergently in bats (fig. S11), the only flying mammalian group. The condensed genomes may represent an adaptation tied to rapid gene regulation required during powered flight (refs 34, 35)." |