X chromosome origin of a supernumerary-like segment in Blatella germanica.
An extraneous heterochromatic segment was discovered in a strain selected for a large-body trait. Derivation from the X chromosome is indicated by its behavior at metaphase I and association with the X and nucleolus in early prophase I. The segment does not pair with the X. Association with a mid-length bivalent is attributed to fusion of heterochromatin. Centromeric activity of small fragments, independent of, but apparently derived from, the X, is also reported.
Department of Entomology, Virginia Polytechnic Institute and State University, 24061, Blacksburg, VA, USA.
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