Nucleotide sequence of the 3'-terminal region of rat 18S ribosomal DNA

The 3'-terminal 230 base-pairs (bp) of the gene for 18S rRNA and 40 bp of the adjoining spacer have been sequenced for the Sprague-Dawley rat. This mammalian sequence has been compared with the known sequences of yeast, fruit fly, silkworm, and frog. This study has shown that the nucleotide-sequence differences between rat and frog are the smallest among and longer species, probably reflecting their evolutionary closeness and longer maturation time compared to the others. There is little similarity in the nucleotide sequences of the transcribed spacer regions of the five species compared.