Into the cells of people and several other organisms the intercourse chromosomes contain a set of chromosomes called the X and Y chromosomes. The X and Y chromosomes had been first found in beetles by Nettie Stevens in 1906. She realized that cells of feminine beetles had identical searching pairs of each and every of these chromosomes that are several but that male beetles had one set when the chromosomes had been different in features from one another. She called those two chromosomes the X in addition to Y, and discovered that female beetles differed from men in containing two X chromosomes. The exact same situation is additionally present in people where females are XX and men are XY.