Barvkar et al. BMC Genomics 2012, 13:175 http://www.biomedcentral.com/1471-2164/13/175 Page 5 of 13 Figure 2 Distribution of introns among 82 UGT genes of Linum usitatissimum. The introns are mapped and numbered to the alignment of their amino acid sequences. It is hypothesized that the introns 3 and 4 were gained prior to diversification of flax UGTs and the gain and loss of other introns in the genes within a phylogenetic group are indicated by the colored mark. The numbers on the top of the map show the intron insertion number occurred on each gene. Intron phases are indicated by blue bar, red open bracket and green close bracket for zero, one and two, respectively.