Life their DNA inside the cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts. In contrast, prokaryotes (bacteria and archaea) store their DNA only in the cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed. DNA was first isolated by Friedrich Miescher in 1869. Its molecular structure was identified by James Watson and Francis Crick in 1953, whose model-building efforts were guided by X-ray diffraction data acquired by Rosalind Franklin. Life is
Francis Crick diffraction images collected by Franklin provided the best evidence for the helical nature of DNA. While Franklin's experimental work proved important to Crick and Watson's development of a correct model, she herself could not realize it at the time. When she left King's College, Director Sir John Randall insisted that all DNA work belonged exclusively to King's and ordered Franklin to not even think about it. Franklin subsequently did superb work in J. D. Bernal's Lab at Birkbeck College with the tobacco mosaic virus extending ideas on helical construction. Crick was often described as very talkative, with Watson – in