Final answer:
The X-ray crystallography of B DNA revealed a double helix structure with a repeating pattern, each nucleotide being separated by 0.34 nm, as seen in Rosalind Franklin's 'Photo 51' which was essential in the discovery of the DNA structure by Watson and Crick.
Step-by-step explanation:
The X-ray screen of the B DNA X-ray crystallography, a method fundamental in determining the atomic and molecular structure of a crystal, showed a diffraction pattern that was pivotal in revealing the double helix structure of DNA. The pattern indicated by X-ray crystallography can yield precise information about the size, shape, and lattice arrangements of atoms within the crystal structure. Scientist Rosalind Franklin's crucial contributions involved taking X-ray diffraction images of DNA, leading to the discovery of DNA's double helix by Watson and Crick. Her work showed a pattern suggesting the consistent, helical shape of the DNA molecule, with a specific repeating structure, where each nucleotide in the spiral was separated by 0.34 nm.
Franklin's X-ray diffraction pattern, known famously as 'Photo 51', demonstrated the regularity and repeated winding structure that is characteristic of the double helix. This discovery was instrumental in understanding the replication of DNA and how genetic information is stored and transmitted in living organisms. It showcased the importance of X-ray crystallography in unravelling the intricacies of biological molecules and set the stage for advancements in molecular biology and related fields.