The nucleotide sequence of a rat 18 S ribosomal ribonucleic acid gene and a proposal for the secondary structure of 18 S ribosomal ribonucleic acid.

The nucleotide sequence of a rat 18 S rRNA gene was determined. The 18 S rRNA encoded in the gene contains 1874 nucleotides, and the molecular weight estimated from the sequence is 6.09 X 10(5). The sequences of rat and Xenopus laevis 18 S rRNAs are very similar; the only differences of consequence are the insertions between nucleotides 197 and 206 and between 258 and 279 of the rat nucleic acid of sequences rich in guanine and cytosine. A proposal is presented for the secondary structure of rat 18 S rRNA based on a comparison with the sequences of 17 other small ribosomal subunit RNAs. While the primary sequences of rat and eubacterial RNAs are different, the deduced secondary structures are remarkably similar.