In the mid-19th century Gregor Mendel carried out breeding experiments on plants
Gregor Mendel observed that the inheritance of each characteristic is determined by ‘units’ that are passed on to descendants unchanged
In the late 19th century behaviour of chromosomes during cell division was observed
In the early 20th century it was observed that chromosomes and Mendel’s ‘units’ behaved in similar ways which led to the idea that the ‘units’, now called genes, were located on chromosomes
In the mid-20th century the structure of DNA was determined and the mechanism of gene function worked out