Formaldehyde fixation of Drosophila testes

This protocol describes formaldehyde fixation of Drosophila testes. The procedure preserves chromosome morphology very well, allowing a clear visualization of the chromosome condensation-decondensation cycle. It also results in excellent preservation of microtubules for immunostaining. The main disadvantage of this fixation technique is its poor preservation of cell morphology, as viewed by phase-contrast optics. In addition, because it involves a rather hard squashing of formaldehyde-fixed testes, it results in meiotic figures which are flatter and larger than those obtained using methanol-acetone or paraformaldehyde fixation protocols.