Immunostaining of Squash Preparations of Chromosomes of Larval Brains

Immunostaining of mitotic chromosomes of larval neuroblasts by antibodies directed against specific proteins is a powerful tool for analyzing their distribution in both euchromatin and heterochromatin. This approach is particularly important for the structural analysis of heterochromatin because the high content of repetitive DNA and the absence of meiotic recombination render this material difficult to manipulate by standard genetic and molecular methods. Sensitive chromosome banding techniques have elaborated a cytogenetic map of Drosophila melanogaster heterochromatin (1 ,2 ), which is now resolved into 61 distinct bands designated h1–h61 (see Chapter 16 ). The relationship between these bands and the locations of 30 genetically defined heterochromatic loci, the major satellite DNA clusters, and 12 different middle repetitive DNA families have been determined (3 ,4 ).