Compositions and methods are provided for restoring function to a non-functional gene product in the genome of a cell. The methods and compositions employ a guide polynucleotide/Cas endonuclease system to restore function to a non-functional gene product and to provide an effective system for modifying or altering target sites within the genome of a plant, plant cell or seed. The present disclosure also describes methods for modifying a nucleotide sequence in the genome of a cell using a restored functional selectable marker, as well as methods for editing a nucleotide sequence in the genome a cell without introducing a polynucleotide modification template into said cell. Compositions and methods are also provided for DNA free delivery of Cas endonucleases, sgRNAs and guide RNA/Cas complexes.
