She had died in 1958, and during her lifetime the DNA structure was not considered to be fully proven. It took Wilkins and his colleagues about seven years to collect enough data to prove and refine the proposed DNA structure. Moreover, its biological significance, as proposed by Watson and Crick, was not established. General acceptance for the DNA double helix and its function did not start until late in the 1950s, leading to Nobel nominations in 1960, 1961, and 1962 for Nobel Prize in Physiology or Medicine, and in 1962 for Nobel Prize in Chemistry. The first breakthrough was from Matthew Meselson and Franklin Stahl in 1958, who experimentally showed the DNA replication of a bacterium Escherichia coli. Now known as Meselson–Stahl experiment, DNA was found to replicate into two double-stranded helices, with each helix having one of the original DNA strands. This DNA replication was firmly established by 1961 after further demonstration in other species, and of the stepwise chemical reaction. According to the 1961 Crick–Monod letter, this experimental proof, along with Wilkins having initiated the DNA diffraction work, were the reasons why Crick felt that Wilkins should be included in the DNA Nobel Prize. In 1962 the Nobel Prize was subsequently awarded to Crick, Watson, and Wilkins. Nobel rules prohibit posthumous nominations or splitting of Prizes more than three ways. The award was for their body of work on nucleic acids and not exclusively for the discovery of the structure of DNA. By the time of the award Wilkins had been working on the structure of DNA for more than 10 years, and had done much to confirm the Watson–Crick model. Crick had been working on the genetic code at Cambridge and Watson had worked on RNA for some years. Watson has suggested that ideally Wilkins and Franklin would have been awarded the Nobel Prize in Chemistry. Aaron Klug, Franklin's colleague and principal beneficiary in her will, was the sole winner of the Nobel Prize in Chemistry 1982, "for his development of crystallographic electron microscopy and his structural elucidation of biologically important nucleic acid-protein complexes." This work was exactly what Franklin had started and which she introduced to Klug, and it is highly plausible that, were she alive, she would have shared the Nobel Prize. Awards and honours Posthumous recognition 1982, Iota Sigma Pi designated Franklin a National Honorary Member. 1992, English Heritage placed a blue plaque commemorating Franklin on the building in Drayton Gardens, London, where she lived until her death. 1993, King's College London renamed the Orchard Residence at their Hampstead Campus as Rosalind Franklin Hall. 1993, King's College London placed a blue plaque on its outside wall bearing the inscription: "R. E. Franklin, R. G. Gosling, A. R. Stokes, M. H. F. Wilkins, H. R. Wilson – King's College London – DNA – X-ray diffraction studies – 1953." 1995, Newnham College, Cambridge opened a graduate residence named Rosalind Franklin Building, and put a bust of her in its garden. 1997, Birkbeck, University of London School of Crystallography opened the Rosalind Franklin Laboratory. 1997, the asteroid discovered in 1997 was named 9241 Rosfranklin. 1998, National Portrait Gallery in London added Rosalind Franklin's portrait next to those of Francis Crick, James Watson and Maurice Wilkins. 1999, the Institute of Physics at Portland Place, London, renamed its theatre as Franklin Lecture Theatre. 2000, King's College London opened the Franklin–Wilkins Building in honour of Franklin's and Wilkins's work at the college. 2001, the American National Cancer Institute established the Rosalind E. Franklin Award for women in cancer research. 2002, the University of Groningen, supported by the European Union, launched