If interons really distract mutagens from hitting exons, wouldn't the
likleyhood of a deletion in an interon/exon increase? Wouldn't this
increase the likleyhood of a frame shift? I would contend that there is
a real function of interons as promotors or the RNA primary transcripts
might have some enzymatic activity. Perhaps they relax the dna to allow
polymerases to move througy more easily. But the contention that they
are sacrificial targets for mutagens seems VERY, VERY weak indeed.