Measurement of the complexity and diversity of poly(adenylic acid) containing messenger RNA from rat liver

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Abstract
The complexity of rat liver poly(A)+ mRNA was measured by analysis of the kinetics of hydridization with both complementary DNA (cDNA) and single copy DNA. The complementary DNA-poly(A)+ mRNA hybridization reaction demonstrates the existence of 3 abundance classes representing 18, 37 and 45% of the cDNA and 4, 290 and 24,000 different 1800-nucleotide sequences, respectively. The poly(A)+ mRNA driven single copy DNA hybridization reaction reveals a single major transition accounting for 1.9% of the haploid rat genome. The kinetics of the poly(A)+ mRNA driven single copy DNA reaction suggest that approximately 45% of the mass of the mRNA population contains over 95% of the complexity. Although higher than previous estimates, the base sequence complexities of rat liver poly(A)+ mRNA measured in these 2 ways are in good agreement, suggesting that the technique of poly(A)+ mRNA-cDNA hybridization may be used in approximating the complexity as well as abundance of a mRNA population. DNA-driven cDNA reactions reveal that about 10% of rat liver poly(A)+ mRNA is transcribed from repetitive sequences in the rat genome.