Cells contain long strands of DNA, which are called chromosomes. Every human cell has 46 chromosomes and all the information that is needed to make us unique human beings is contained in these chromosomes. DNA itself is made up of a series of compounds called nucleic acids. The sequence tells the organism what to make, when to make it, and where to make it. Each person is unique because the nucleic acids of his or her DNA are arranged differently.
Simple traits come from complex genes.
This illustration shows how the gene that determines flower color is created. Take, for example, the gene for flower color. The arrangement of the nucleic acid compounds on a chromosome in one plant tells the flower cells to produce certain proteins that make the flower blue. On another plant, the nucleic acid compounds are arranged differently, instructing the plant to make pink flowers. Eye color in humans is similar.