Who is at Risk for FAP?
Each child of a parent with FAP or attenuated FAP has a 50 per cent risk of inheriting the disease gene. If an affected parent has four children, this does not mean that two children will have FAP. The chances are the same in each pregnancy that the FAP gene will be passed on by the parent with FAP. FAP affects males and females of every race and ethnic group. FAP does not skip generations.
In the past, neither doctors nor scientists could predict who would be diagnosed with FAP until adenomas developed in the large intestine. However, in 1991, the gene responsible for FAP was discovered and was named the Adenomatous Polyposis Coli, or APC, gene.
Genes are the units of heredity which decide our sex, eye/hair colour, build, and, sometimes, susceptibility for certain diseases. We now know that about 100,000 genes do their work inside each human cell. Genes contain all the information the cell needs to carry on its production of protein and energy, like an encyclopedia.
Deoxyribonucleic acid, or DNA, is the language of the genes, the master chemical. When cells divide, the genes and DNA copy themselves. Genes are found in separate strands of DNA called chromosomes. We inherit 23 pairs of chromosomes and one member of each pair comes from each parent.
When copying takes place perfectly, genetic information is passed from one generation to the next. However, if even a tiny change occurs, either the structure or the functions in the body may be dramatically different. For example, the word "milk" makes perfect sense until one letter is switched: "xilk". This change is called a mutation. If left unrepaired, the change is passed on and can contribute to a particular disease.
Diagram of DNA, a molecule carrying genetic information
(Reproduced with permission by Jeanne C. Kelly, Aardvark Design Associates.
Original artwork for the National Cancer Institute, Bethesda, Maryland.)