While determining the sequence of the genomic regions of
ced-3 ,
ced-9 and
unc-50 ,several classes of inverted repeats were discovered in non-coding regions both upstream of the
ced-3 start site and within some of the introns (see article this issue by Shaham and Horvitz). We searched the GenBank database for similar sequences using the "Blast" program and identified three sequences similar to other regions of the C. elegans genome. The sequence comparisons of these various repeats are shown below. Repeats a and c [See Figres 1 & 2] are found as inverted repeats, thus, we have compared each arm (forward) to its partner (reverse) and to the other sequences. Repeat d [See Figure 3] was found as a single (as opposed to inverted) repeat in both
ced-3 and
lin-12 .The four largest introns of
ced-3 contain repetitive elements, suggesting that large introns (>200 bp) in C. elegans might be a consequence of the presence of defective transposons, which might not affect the function of the gene. We are interested in obtaining more information concerning these or other repeats in other regions of the genome.