Increased Risk

As with all genes, cancer suppressor genes have two copies, each in a different DNA molecule.

In sporadic (non-hereditary) cancers linked to a suppressor gene, only when both alleles (gene copies) are changed is the gene considered non-functional (mutated). This means that the process has to be done in two steps. (1 allele at the time)

In the case of a hereditary cancer, however, one of the gene copies is already inherited mutated. This increases dramatically the risk of disease, as now only one new mutated copy is needed for the gene to stop working. 

In the case of a hereditary cancer, however, one of the gene copies is already inherited mutated. This increases dramatically the risk of disease, as now only one new mutated copy is needed for the gene to stop working. 

This second mutation can emerge at any time during the individual’s life, in one or more cells, but also might never happen. 

                                                                     
Important - the mutation will only have an effect in those cells where the gene is active .