What are DNA, chromosomes and genes?
The fundamental pattern for the physical traits of a human being (or any life form) is found in a complex chemical called deoxyribonucleic acid, or DNA, which is formed of four molecules called bases, bound together by a framework of other molecules (sugars and phosphates) in a structure which looks something like a twisted ladder — the so-called double helix. The four different bases are called adenine, cytosine, guanine and thymine, abbreviated A, C, G and T respectively. They are strung out along the legs of the ladder, with chemical bonds between opposite pairs forming the rungs. It is the order of these bases along the ladder which determines all of the features and attributes of the human being. Most human DNA is organized into strands called chromosomes, and along each chromosome are many shorter sections called genes. There are forty-six different human chromosomes, and they are joined together in twenty-three chromosome pairs, with one member of each pair inherited from the
