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
Rudolf Signer from the Thymus of calves, of which he took 15 grams of extraordinarily pure DNA to London. In England he gave it to various scientists, among them Maurice Wilkins, in order to promote research in the field. The analysis of X ray images of these DNA samples in Wilkins' laboratory allowed James Watson and Francis Crick to discover the double-helix structure of DNA. Rests of the DNA which Signer brought to England, survive today in the collection of King's College, London. Over 250 of Signer's scientific writings were published during his lifetime. The Lavoisier Medal was awarded to him for