Information is stored in existing DNA through an iterative process of creating a break in dsDNA and adding new DNA by repairing the break with a homologous repair template. The order and sequence of DNA sequences added to the breaks in the dsDNA can encode binary data. By using a context-dependent encoding scheme, three unique homologous repair templates can encode an unbounded number of bits. When the existing DNA is in a cell, the changes are heritably passed to subsequent generations of the cell. Synthesis of the homologous repair templates may be under the control of a promoter and operator. Intra- or extra-cellular signals may regulate the synthesis of homologous repair templates.