The initial thrust of genetic research is the treatment and potential cure of genetic illnesses. Therefore, we must explore why genetic illnesses occur at all. The first level and usually the easier of the two are the scientific. Mutations are mistakes in the DNA sequence. Sometimes a mutation is simply the substitution of one nucleotide for another.
Mutations can also result from a piece of DNA being deleted.
This may cause one or more codons to disappear. This causes the severe respiratory and digestive problems of CF patients that are usually lethal before their 30th birthday. So far, genes for more than 1,200 human disorders have been identified, which are found over all twenty-three pairs of human chromosomes. Some estimate that there may be as many as 3,000 to 4,000 human genetic disorders that are due to defects in a single gene. Most disorders, however, will be due to mutations in a host of genes.