Before the 1940s, scientists knew about genes and other inherited materials, but many believed that proteins, not DNA, were the molecules responsible. Their reasoning seemed logical at that time: Proteins are a major constituent of all cells and come in a wide array of functions and varieties, so it would make sense that this was one more protein controlling yet another function: our genetic makeup. In addition, a great deal more was known about the structure and function of proteins than about DNA. It was not until scientists began to look deeper into the DNA molecule that its true nature, so to speak, was found.