Figure 1.

Sequence patterns at the 5′ and 3′ splice sites of introns in Populus. Relative occurrence of different nucleotides at the donor (exon-intron) and acceptor (intron-exon) junctions of ROS-related genes of Populus. The start and end of introns are GT and AG, respectively, which are found to be conserved (at positions 1 and 2 at the exon-intron boundaries and at positions −2 and −1 at the intron-exon boundaries, respectively). This image was produced by extracting 10 nucleotides (five from the exon and five from the intron) at the 5′ and 3′ splice sites of 165 introns from the annotated sequences of selected genes.