Chromosome Conjugation in Hybrids between Drosophila melanogaster and Drosophila simulans

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Abstract
In the salivary gland cells of fully grown [female] larvae of melanogaster-simulans hybrids all the chromosomes showed a lessened tendency to conjugate, especially at their distal ends; in the X-chromosome failure to conjugate was apparent at the distal end only, for the length of 10 to 11 bands. In the controls conjugation was practically complete. Corroboration of the fact of weaker conjugation in the hybrids was derived from a study of loop formation in individuals heterozygous for the inversion delta-49 (i.e., melanogaster-simulans hybrids containing this inversion from the X-chromosome of D. melanogaster) the conjugation in the region of the inversion was confined to a short section and, within this section, incomplete; while in [female][female] of D. melanogaster heterozygous for the delta-49 inversion, or other inversions, chromosomes nearly always conjugated completely, in both inverted and non-inverted regions, even up to the point of re-arrangement. Possible explanations of the weaker con-jugation in hybrids are discussed.