Nucleic acid molecules encoding dna modifying enzymes and active fragments and variants thereof and compositions comprising the same

A method for modifying a target DNA molecule, said method comprising delivering a system comprising:

• a) a fusion protein comprising a Type II CRISPR-Cas protein nickase and a deaminase, wherein said deaminase comprises an amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO:
• 407 and has adenine deaminase activity, and wherein said nickase
• (i) is a Cas9 nickase;
• or
• (ii) comprises an amino acid sequence having at least 95% sequence identity to any one of SEQ ID NO:
• 42, 52, 53, 55-59, 61, 397, or 398;
• and
• b) one or more guide RNAs (gRNAs) capable of hybridizing to said target DNA molecule or one or more nucleotide sequences encoding the one or more gRNAs;
• to said target DNA molecule or a cell comprising the target DNA molecule, wherein the one or more gRNAs are capable of forming a complex with the fusion protein in order to direct said fusion protein to bind to and modify said target DNA molecule.