Chromosomal differentiations of the lampbrush type formed by the Y chromosome in Drosophila hydei and Drosophila neohydei.
The nuclei of growing spermatocytes in Drosophila hydei and D. neohydei are characterized by the appearance of phase-specific, paired, loop-shaped structures thought to be similar to the loops in lampbrush chromosomes of amphibian oocytes. In X/O-males of D. hydei spermatogenesis is completely blocked before the first maturation division. No spermatozoa are formed in such testes. In the nuclei of X/O-spermatocytes, paired loop formations are absent. This shows the dependence of these chromosomal functional structures upon the Y chromosome. The basis of this dependence could be shown through an investigation of males with two Y chromosomes. All loop pairs are present in duplicate in XYY males. This proves that the intranuclear formations are structural modifications of the Y chromosome itself. These functional structures are species-specific and characteristically different in Drosophila hydei and D. neohydei. Reciprocal species crosses and a backcross showed that the spermatocyte nuclei of all hybrid males possess the functional structures corresponding to the species which donated the Y chromosome. This shows that the morphological character of the functional structures is also determined by the Y chromosome.
D000818:Animals; D002467:Cell Nucleus; D002875:Chromosomes; D004330:Drosophila; D005854:Germ Cells; D008297:Male; D013090:Spermatocytes; D013091:Spermatogenesis; D013094:Spermatozoa; D014998:Y Chromosome
CELL NUCLEUS; CHROMOSOMES; DROSOPHILA; GERM CELLS