We have determined the DNA sequences encoding 18 S ribosomal RNA in @entity1 and in the frog, @entity1238 borealis. We have also corrected the @entity1238 18 S sequence: an A residue follows G-684 in the sequence. These and other available data provide a number of representative examples of variation in primary structure and secondary modification of 18 S ribosomal RNA between different groups of vertebrates. First, @entity1238 and @entity1238 borealis 18 S ribosomal genes differ from each other by only two base substitutions, and we have found no evidence of intraspecies heterogeneity within the 18 S ribosomal DNA of @entity1238 (in contrast to the @entity1238 transcribed spacers). Second, the @entity1 18 S sequence differs from that of @entity1238 by approx. 6.5%. About 4% of the differences are single base changes; the remainder comprise insertions in the @entity1 sequence and other changes affecting several @entity2036 . Most of these more extensive changes are clustered in a relatively short region between nucleotides 190 and 280 in the @entity1 sequence. Third, the @entity1 18 S sequence differs from non-primate @entity1 sequences by only about 1%. Fourth, nearly all of the 47 @entity5498 groups in @entity1 18 S ribosomal RNA can be located in the sequence. The @entity5498 group distribution corresponds closely to that in @entity1238 , but there are several extra @entity5498 groups in @entity1 18 S ribosomal RNA. Finally, minor revisions are made to the estimated numbers of pseudouridines in @entity1 and @entity1238 18 S ribosomal RNA.

XXXX 18 S ribosomal RNA sequence inferred from DNA sequence. Variations in 18 S sequences and secondary modification patterns between vertebrates.

@entity1 :: ('9606', 'Species') :: ['mammalian', 'human', 'man'] @entity5498 :: ('CHEBI:32875', 'Chemical') :: ['methyl'] @entity1238 :: ('8355', 'Species') :: ['Xenopus laevis', 'Xenopus'] @entity2036 :: ('MESH:D009711', 'Chemical') :: ['nucleotides']
@entity1 :: (9606,Species) :: ['Human']
