A simple solution might be to seek stop codons in regions
along the sequence. Clearly, if several
stop codons appear close to each other in a region, it
cannot be a coding region, since it would have been terminated. When a relatively long sequence does
not contain stop codons, it becomes more probable that it contains a coding region. The
problem becomes more complex in eukaryotic DNA due to the existence of interleaved
exons and introns. In that case, a stop codon does not indicate that the sequence
is not in a gene, but merely that the sequence is not in an exon. Further complications
arise from the fact that a certain DNA sequence can be interpreted in 6 different
ways: 3 different offsets for each of the possible 'starting points' (the reading
frame of the codons) times two for the reading direction. It is safe to assume
that in most cases, apart from prokaryotic species, a DNA region will encode
only one gene.