An interspersed region of the sea urchin genome represented in both maternal poly(A) RNA and embryo nuclear RNA.
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The sequence organization and transcriptional expression of a 17-kb region of the Strongylocentrotus purpuratus genome are described in this report. This region includes a transcription unit, designated "gene 88," that is represented by a typical low prevalence maternal poly(A) RNA. The predominant maternal gene 88 transcript is about 9.5 kb in length, and analysis of the sequence organization of the cloned genomic region encoding this transcript shows that it contains a high density of low and moderately prevalent repeat sequences, as well as 2 kb of single-copy sequence. Genome blots carried out with DNA from different individual sea urchins show that several allelic forms of this single-copy region exist. The transcribed single-copy sequence is only slightly less polymorphic than is the average single-copy sequence of the S. purpuratus genome. Gene 88 single-copy sequences appear to be represented in at least three smaller transcripts in the polysomal RNA of 16-cell embryos. The nuclear RNA of later embryos also contains gene 88 transcripts. RNA gel blots indicate that polyadenylated gene 88 transcripts are also 9.5 kb in length in blastula and gastrula nuclear RNAs and these transcripts are probably colinear with the major maternal RNA transcript. 1982.