Bidirectional unique map between human and mouse segments (exons or introns)

  The columns are:
  1) chr_beg_end_strand = segment coordinate in the genome. 
	Note that (i) if strand < 0 then beg > end, and 
		 (ii) positions always refer to the first or the last exonic nucleotide, also for introns 
  2) segment_type (1=exon, 2=intron)
  3) gene_id
  4) gene_class
  5) position_within_transcript (1=initial, 2=internal, 3=terminal)
  6) prediction_level (0=predicted from SJ, 1=annotated); note that only introns but not exons can be predicted from SJ
  7) alternative_status (0=alternative, 1=constitutive)
  8-14) contain the same information as 1-7 but in mouse
  15) mapping_status (0 = annotated in both, -1 = predicted in human by mouse support, 1 = predicted in mouse by human support)

For instance, in order to get the orthologous list of annotated exons, do 
   awk '$2==1 && $15==0' data/hg19.mm9.bum_r.tab