Genome instability (also genetic instability or genomic instability) refers to a high frequency of mutations within the genome of a cellular lineage. These mutations can include changes in nucleic acid sequences, chromosomal rearrangements or aneuploidy. Genome instability does occur in bacteria.

Genomic instability is the result of gradual damage to DNA in ways that are not naturally repaired. This is a root cause of aging, and it leads to genetic mutations and an increased risk of cancer.

The cells of your body produce a constant flow of proteins and other materials; these are built according to the blueprints contained in our DNA and are vital to cell function and survival. A large amount of information contained in the DNA is ignored during this process, and this is thought to be junk DNA, remnants of our evolutionary past that are no longer used. DNA damage can affect genes and their transcription, resulting in dysfunctional cells that, if not destroyed by apoptosis, a kind of self-destruct mechanism which activates when a cell is too heavily damaged, may jeopardize tissue and host homeostasis.