Francis Crick DNA crystals revealed to Crick that the two DNA strands were antiparallel. In January 1953, Watson was shown an X-ray photograph of B-DNA (called photograph 51), by Wilkins. Wilkins had been given photograph 51 by Rosalind Franklin's Ph.D. student Raymond Gosling. Wilkins and Gosling had worked together in the Medical Research Council's (MRC) Biophysics Unit before director John Randall appointed Franklin to take over both DNA diffraction work and guidance of Gosling's thesis. It appears that Randall did not communicate effectively with them about Franklin's appointment, contributing to confusion and friction between Wilkins and Franklin. In the middle of February
Z-DNA as a left-handed double helix with two antiparallel chains that were held together by Watson–Crick base pairs (see X-ray crystallography). It was solved by Andrew Wang, Alexander Rich, and coworkers in 1979 at MIT. The crystallisation of a B- to Z-DNA junction in 2005 provided a better understanding of the potential role Z-DNA plays in cells. Whenever a segment of Z-DNA forms, there must be B–Z junctions at its two ends, interfacing it to the B-form of DNA found in the rest of the genome. In 2007, the RNA version of Z-DNA, Z-RNA, was described as a transformed version of