| Exon foud by aligning to the mouse genome (NCBI build
 36, Feb.
2006), with a mininum allowed exon length of 20nt and a minimum allowed
intron size of 50nt, the following: 
 
        48,360
unique IRC sequences. From those, 47,927 IRC
sequences whose best alignment with a chromosome involves at least 50%
of the IRC sequence were taken for exon-tiling.10,471 RefSeq sequences not contained in the exon
collection obtained in step 1 (according to blat alignments). From those, 10,095 RefSeq sequences
whose best alignment with a chromosome involves at least 50% of the
RefSeq
sequence were taken for exon-tiling.11,257 Ensembl transcripts (9,831 Ensembl genes) not
contained in the exon collection obtained in steps 1 and 2 (according to MGI-Ensembl tables provided by MGI). From those,
11,110 transcripts whose best alignment with a chromosome involves at
least 50% of the transcript sequence were taken for exon-tiling. 
        
          
            | Source | Number of
sequences taken for exon-tiling | Number of
Exons obtained | Median Number of Exons per sequence | Mean Number of Exons per Sequence | Maximum Number of Exons per Sequence |  
            | IRC | 47,927 | 353,809 | 5 | 7.38 | 155 |  
            | RefSeq | 10,095 | 25,199 | 2 | 2.49 | 79 |  
            | Ensembl | 11,110 | 54,365 | 2 | 4.89 | 147 |  
            | Total | 69,132 | 433,373 | 4 | 6.27 | 155 |  |