Compositions having polynucleotides encoding multiple translational stop
signals in more than one reading frame are provided. The compositions
include isolated polynucleotides, expression cassettes, and vectors, as
well as host cells, prokaryotic organisms, and eukaryotic organisms
comprising the polynucleotide(s). Methods include using the
polynucleotides to stop translation of an mRNA into a protein, to produce
a transformed cell and/or organism comprising the polynucleotide, and to
identify transformed cells or organisms of a specific lineage.