Monocentric elements containing two doses of the X chromosome. Drosophila females carrying attached X chromosomes usually also have a Y chromosome. They produce XX and Y eggs and therefore generate patroclinous sons (which inherit their X from their father and their Y from their mother) and matroclinous daughters (which inherit their X from their mother and their Y from their father). The terms double X and compound X are also used for aberrant chromosomes of this types. See Chronology, 1922, Morgan; detached X.
Subjects: Genetics and Genomics.