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. One person's genes produce proteins that make eyes brown, while another person's genes produce proteins that make eyes blue. Many genes interact to produce the right proteins, which generate these traits.
Some genes have control regions on the chromosome.
These region are like a light switch or a thermostat. They turn the gene on or off, or regulate the amount of protein produced. While cells carry identical DNA codes, different cells have different functions. For example, the cells of your fingertips do not need to make the proteins that color your eyes. The gene for eye color protein is turned on in your eyes and turned off in your fingertips.