The Responding Site of the Rex Locus of Drosophila melanogaster.
Rex is a dominant, maternal-effect locus in the heterochromatin of the X chromosome Drosophila melanogaster. It causes an early mitotic exchange-like event between heterochromatic elements of an attached- XY in X/attached-XY embryos of Rex mothers. Evidence is presented here that the site of Rex action is the ribosomal RNA gene cluster (the bb locus) only; no other heterochromatin is affected. The Rex locus may be useful in studying regulation of rRNA-gene copy number, mitotic chromosome behavior and heterochromatic function.
Swanson
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Genetics Program, Michigan State University, East Lansing, Michigan 48824-1320.