THE DNA components of the chicken genome

The organization of the chicken genome was investigated by centrifuging chicken DNA (Mr = 57 X 10(6) in preparative Cs2SO4/Ag+ and Cs2SO4/BAMD density gradients [BAMD = 3.6-bis(acetato-mercurimethyl)dioxane]. An analysis by CsCl density gradient of the DNA fractions obtained from the preparative experiments revealed that 88% of the genome is made up of four DNA components, characterized by buoyant densities of 1.699, 1.702(5), 1.704(5) and 1.708 g/cm3 and representing 39%, 25%, 15%, and 9%, respectively, of the total DNA. The remaining 12% of the genome is formed by seven minor and/or satellite components. The distribution of the ovalbumin gene in a Cs2CO4/BAMD density gradient, as tested with a cloned cDNA probe, coincides with the distribution of the 1.702(5)-g/cm3 component. This shows that the DNA regions flanking the ovalbumin gene are homogeneous in base composition over along distances and that the gene is located on a DNA segment belonging to the 1.702(5)-g/cm3 component.