SB then integrates into random sites within the genome, although some studies report very slight preferences for transcriptional units.

We have found evidence for a large number of transcriptional units (65,000-75,000) and performed initial annotation and classification.

While our estimate of 65,000-75,000 transcriptional units clearly differs from these estimates, it is useful to consider that there is much independent agreement in the reports.

A total of 9,372 transcriptional units were based on singleton transcripts without splicing evidence.

Together, a total of 75,982 transcriptional units were placed on the genome, providing an initial glimpse of a complete gene map.

As a conservative correction for the possibility that separate transcriptional units might belong to the same gene, we considered successive distances for every other transcript.

The availability of emerging mouse genomic sequence allowed us to examine sequence conservation across the transcriptional unit.

In mammals, three miR-34 precursors are produced from two transcriptional units.

Eight mutations have been identified- four are nonsense mutations, one is a deletion that includes most of the transcriptional unit.

Discussion Our bioinformatics approach identified 217 candidate instances of overlapping transcriptional units in the human and mouse genomes.