Abstract
DURING the early determination of the blastomeres in the nematode Ascaris chromosomal segments are eliminated in the presomatic cells (chromatin diminution). In the germline, however, all the chromatin is preserved. Similar genome differentiation phenomena have been published1–3. Since no molecular description of chromatin diminution has been made we have begun to study the chromosomes in germline and somatic cells4. It was found that the amount of DNA occurring only in the germ-line chromosomes is not constant5 and that this DNA is not enriched in rDNA6. There is no evidence that the germline-limited DNA is transcribed in vivo7. The results presented here show that the germline DNA of Ascaris contains highly repetitive components, eliminated by the diminution process. Their possible molecular function in connection with germline–soma differentiation and chromosomal behaviour is discussed.
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