The principal goals of this project are: 1) to determine the various 3-dimensional structures adopted by chromosomes at different points in the cell cycle; 2) to work out the physico chemical basis underlying their stability; and 3) to show how these satisfy the functional requirements of cell division, recombination, gene expression and replication. Dr. Widom has developed a new kind of X-ray "area" detector which shows significantly improved resolution. This will be used to obtain diffraction patterns from semi-oriented samples of chromosomes in various stages of folding, from which structural information may be deduced. He will also use yeast genetics to identify proteins (and their genes) that are necessary for the final stages of chromosomal folding, for cell division and recombination.***//