The molecule that is responsible for heredity traits is DNA (deoxyribonucleic acid). DNA is a long, double-stranded helical molecule that contains the genetic information necessary for the growth, development, and reproduction of all living organisms. The sequence of DNA nucleotides (adenine, thymine, cytosine, and guanine) determines the genetic code that specifies the sequence of amino acids in proteins. This sequence of amino acids determines the structure and function of proteins, which in turn determine the physical characteristics and traits of an organism. DNA is passed down from one generation to the next, providing the basis for heredity and the transmission of genetic traits from parents to offspring.