1962 M. H. F.WILKIN S 



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Fig. 4. X-ray diffraction pattern of cephalopod sperm. The DNA molecules in the 



sperm heads have their axes vertical. The 3.4 A internucleotide spacing corresponds to 



the strong diffraction at the top and bottom of the pattern. The sharp reflections m the 



central part of the pattern show that the molecules are in crystalline array. 



pared the DNA in order to compare the DNA of normal and leukaemic 

 leucocytes. The DNA gave a very well-defined X-ray pattern. Thus began 

 a collaboration that has lasted over many years and in which we have used 

 Hamilton's DNA, in the form of many salts, to establish the correctness of 

 the double-helix structure. Hamilton prepared DNA from a very wide 

 range of species and diverse tissues. Thus it has been shown that the DNA 



s-41 



