Gene length and alternative transcription in fruit fly

Alternative transcription, in which a single gene may give rise to multiple variant mRNA forms, is widely recognized as an important source of protein diversity in complex, eukaryotic genomes. Here we show that in the Drosophila genome, larger genes with greater numbers of exons tend to be alternatively transcribed to a greater degree than smaller genes with fewer exons. In addition, we show that a log-normal distribution provides a good approximation for gene length distributions in Drosophila and that an exponential function relates the number of variants produced per gene with average exon count.