Worm Breeder's Gazette 8(3): 69

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

The Sequence of One C. elegans rDNA Repeat Unit

A. Coulson, R.E. Ellis

We have determined the complete nucleotide sequence of one ribosomal 
DNA tandem repeat (that cloned originally by J. Files and D. Hirsh as 
pCe7).  Furthermore, in comparing this data with partial sequence data 
obtained from three separately isolated rDNA clones, we have seen 
almost no sequence variation, indicating the highly homogeneous nature 
of the rDNA repeat population in C.  elegans.  Preliminary examination 
of the sequence has confirmed the size and location of the genes for 
each of the rRNA species produced, as predicted by visualization of R-
loops (Files and Hirsh).  The 26s and 18s rDNA genes each show the 
expected pattern of several long stretches of sequence very homologous 
to that in the rDNA of other eukaryotic organisms, interrupted by 
short regions with no significant homology.  The 5.8s rDNA gene has 
also been located, and the sequence of its RNA product shows the 
expected pairing between its 3' end and the 5' end of the 26s rRNA.  
We are currently running a more detailed study of the relationships 
between the 26s, 18s, and 5.8s rRNA molecules of C.  elegans, as 
inferred from this sequence, and those of other eukaryotes, especially 
as this relates to the secondary structure of these molecules.