Why is a carcinogenic mutation not inheritable?

Answer 1

Not all mutations that occur are inheritable. Inheritable means that the mutations are able to be passed on from an organism to the organism's offspring. Only mutations that occur on the gametes (sex cells) are inheritable. For example, if a mutation occurs in a somatic cell (body cell), the mutation will never be inherited by the organism's offspring because that mutation is not part of the cells that pass on genetic information to offspring. Somatic cells only create new cells for the individual's body, whereas gametes have the ability to be passed on to offspring.

Answer 2

Many mutations are actually benign. They may occur in areas of DNA which don't code for anything, or a mutation may occur in a gene that isn't expressed (ie, isn't "turned on" and being used to make proteins) in that particular cell.

Even when a mutation occurs in an expressed gene, it may still be benign since different codons can translate into the same amino acid. For instance, the DNA sequences 'GGA' and 'GGC' both code for the amino acid proline. This means that a mutation from 'GGA' to 'GGC' would still cause the same amino acid to be synthesized, and no bad effect would result.

Even when a mutation is harmful, the result isn't always cancer. Many other diseases, such as hemophilia and Huntington's disease, are genetic and would have first come about as mutations. Cancer occurs when mutations happen in genes that control cell growth, division, and death.