To study the distribution of transposition events of Tgm9 across the chromosomes, the physical locations of the Tgm9 insertion sites in the soybean genome were investigated. Although Tgm9-insertion in promoters can alter phenotypes, due to the limitation in precisely predicting the promoter sequences we calculated the number of insertions that were localized to only exon- and intron-sequences. These mutations are expected to knock-out gene function, and therefore are desired mutations for functional analyses of soybean genes. Of the 105 insertions studied, 16.2% and 9.5% of the Tgm9-insertions were localized to exons and introns, respectively (Fig 3, S3 Table). Thus, 25.7% of the insertions were generated in gene-sequences. In the soybean genome, gene-sequences cover 22.1% of the genome (S3 Table), which is very comparable to the observed insertion rate of 25.7% in the gene-sequences. The calculated χ2 value (1.92 at df = 1) suggests that the observed frequencies of Tgm9 insertions in exons and introns (Fig 3) is statistically not significant at p = 0.05 from the expected values resulting from random insertion of the element in exon and intron sequences. We therefore conclude based on the study of 105 mutants that the Tgm9 element appears to transpose randomly in the soybean genome (Fig 3, S3 Table).