The chromosomes of plant and animal cells are composed of DNA, the genetic material, and an equal mass of protein. These chromosomes participate in two major functions: they are replicated precisely preceding cell division, and they serve as the template for information (in the form of RNA and ultimately protein) used by the cell for metabolism and growth. One of the current areas of intense research interest in Cell Biology concerns the role and importance of DNA-protein structure in the processes of replication and information transfer. This proposal combines techniques from biochemistry, immunology, electron microscopy, and molecular genetics to study chromosome structure and function. The experimental system being used in the proposed research is unique, and particulary well suited for the problems being studied. The ciliated protozoan, Euplotes, contains two types of nuclei: the micronucleus, which acts as a storehouse of germline genetic information, but is metabolically inactive, and the macronucleus, which contains the active genes of the cell. The macronuclear chromosomes are unusual in that they have somehow been digested to yield short, linear, gene-sized DNA fragments. This property is of significant importance for an analysis of gene expression. These chromosomes also contain a dynamic structure called the replication band that becomes especially useful for studying their duplication.
