Physical mapping of the Tgm9 insertion sites among 105 mutants revealed that the element transposes to all 20 chromosomes (Fig 2). Insertion sites per chromosome ranged from 1 to 16 per chromosome (Fig 2). These vast differences in the distribution of insertions among chromosomes could be due to the small sample size of the population studied or due to a preference of the element to transpose into some genomic regions. There were six genomic regions, <1 Mb in size, which were enriched in Tgm9 insertions. Of the 105 identified mutants, 24 were mapped to these six regions: (i) Chromosome 1 (six Tgm9 insertions between 50.06 and 50.50 Mb region (http://www.soybase.org/SequenceIntro.php); (ii) Chromosome 9 (four between 4.07 and 5.07 Mb); (iii) Chromosome 9 (five between 8.77 and 9.06 Mb), (iv) Chromosome 15 (three between 2.58 and 2.87 Mb); (v) Chromosome 17 (three between 40.65 and 40.89 Mb); and (vi) Chromosome 18 (three between 54.31 and 54.51 Mb) (Fig 2). In soybean the euchromatic region constitutes 43% of the genome . In this study, Tgm9 transposed to euchromatic regions 77.1% of the time. The remaining 22.9% of insertions were mapped to the pericentromeric regions (Fig 2).