How was it concluded that genes are located on chromosomes?

Morgan confirmed the Mendelian laws of inheritance and the fact that genes are located on same chromosomes. Morgan had discovered that eye colour in Dorsophilia expressed a sex linked trait. All first generation offspring of a mutant white-eyed male and a normal red-eyed female would have red eyes because every chromosome pair would contain at least on copy of the X chromosome with dominant trait. The X chromosome is transferred to both male and female offspring because Dorsophilia exhibits XY type of sex determination.