As you probably already know, the English language consists of a 26-letter alphabet. According to Dr. John Stamatoyannopoulos, U Washington associate professor of genome sciences and of medicine, DNA has a 64-letter (or codon) alphabet that spells out the genetic code. These codon letters are organized into words and sentences called genes - a segment of DNA passed down from parents to child that confers a trait to the offspring. Humans have 25,000-30,000 genes, usually in pairs (one from each parent). A mutation is a change in the spelling of the codon letters in a DNA sequence. Every person’s DNA contains mutations that typically are quite harmless. Some mutations, however, may be responsible for triggering abnormal conditions and specific diseases. Sickle cell anemia, for example, reportedly can be caused by a change in one single gene.