Hemophilia is due to lack of genes that govern production of s specific clotting factor. Dawn syndrome or Mongolism is also a genetic disorder. Gene replacement therapy has been successful in a handful of conditions, whereby an abnormal gene is substituted with a normal one. The process of substituting abnormal genes is a very difficult and complicated one. This method of treatment is not widely available either.
Genes have many different functions.
As far as their role in cancer goes, there are genes that control the development and growth of cells. Certain genes promote and certain genes inhibit cell growth. There has been a great degree of hype about genetic cancer treatment. This technology is still at its infancy and has not been even properly tested to see whether it works. We still need to expand our knowledge about the genetic controls and the function of the genes within cancer cells.