Developmentally important genes in D. melanogaster have larger intergenic intervals than their C. elegans counterparts. (a) Forty-nine developmentally important genes from D. melanogaster and their C. elegans counterparts. Genes in the top section represent orthologs, defined by KOG. Subsequent sections represent gene families. Listing of genes in different species on the same line within gene families does not imply that they are orthologous. The mean intergenic size for the D. melanogaster genes is 27,928 bp. Then mean intergenic size for the C. elegans genes is 7,670 bp. (b) Genomic regions of four representative gene sets in D. melanogaster (red) and C. elegans (blue). Orange boxes designate exons of the indicated genes. Gray boxes designate exons of neighboring genes. Note that genomic intervals are typically larger in D. melanogaster than in C. elegans, often owing to both larger flanking noncoding regions and larger introns. The total euchromatic genome of D. melanogaster is estimated at 117 Mb and the euchromatic genome of C. elegans is estimated at 100 Mb. The overall gene distribution within the genome is denser in flies than worms, suggesting that the larger regions of noncoding DNA associated with these representative complex genes are specifically allocated to these loci.
Nelson et al. Genome Biology 2004 5:R25