Size heterogeneity of ribosomal RNA in eukaryote evolution—1. rRNA molecular weights in species containing intact large ribosomal subunit RNA

Abstract

1. 1. The molecular weights of the two major rRNA species (L-rRNA, large ribosomal subunit RNA, and S-rRNA, small ribosomal subunit RNA) of a variety of deuterostomia, green plants and fungi have been investigated by gel electrophoresis in 99% formamide, pH 9; the overall pattern obtained under these conditions differs to some extent from that deduced by electrophoresis in neutral-salt solutions. 2. 2. The molecular weights of the deuterostomian S-rRNA species have been conserved at a value of 0.65 × 10 6 , whereas those of the L-rRNA have been kept at 1.40 × 10 6 in the lower species but have increased to 1.55 × 10 6 in birds and to 1.65 × 10 6 in mammals. 3. 3. The molecular weights of the L-rRNA and S-rRNA components of the green plants (Dycotyledons, Monocotyledons and Gymnosperms) have been generally conserved at 1.30 × 10 6 and 0.65 × 10 6 . 4. 4. The molecular weight of the L-rRNA of the fungi has been conserved at 1.36–1.38 × 10 6 , being 0.1 × 10 6 daltons heavier than that of the plants; the S-rRNA exhibits a limited degree of variability, ranging between 0.65 × 10 6 and 0.72 × 10 6 .