Organization of Nucleotide Sequences in the Chicken Genome

The four major components of chicken DNA were prepared by density gradient centrifugation and characterized in several basic properties: relative amounts, dG + dC content, buoyant densities, compositional heterogeneity, and reassociation kinetics. While the relative amounts and the compositions of the major components of chicken DNA were similar to those found in mammalian genomes, their compositional heterogeneities were found to be narrower. The relative amounts of interspersed repeated and unique sequences were strikingly different in different components and also different from those found in the corresponding major components of mouse and human DNAs. If one takes into consideration that major DNA components (a) account for practically all of main‐band DNA and (b) derive by preparative breakage from vey long DNA segments of fairly homogeneous composition, the isochores, our findings indicate that the distribution of interspersed repeats is different chromosomal regions and is species‐specific.