Complexity and specificity of polysomal poly(A+) RNA in mouse tissues.

Base sequence complexities of polysomal poly(A+)RNA from mouse embryo, brain, and liver have been estimated by hybridization to homologous cDNA to be approximately 7 x 109, 1.5 x 1010, and 7 x109 daltons, respectively. By annealing each cDNA with a large excess of total mouse embryo DNA, the genes coding for the polysomal poly(A+) sequences were shown to be unique. Heterologous hybridization experiments showed that the high abundance class of poly(A+) sequences in one tissue is not identical with the high abundance class in other tissues. However, at least 55%, and possibly more, of the poly(A+) RNA in one tissue is present in the poly(A+) RNA of another tissue.