OBJECTIVE OF THE EXPERIMENT The objective of the experiment detailed below is to study the function of the Drosophila gene apterous (ap) in the development of the wing in clones of mutant cells (Díaz-Benjumea and Cohen, 1993). The analysis of this experiment is a way to introduce the concept of an organizer center in development.

DEGREE OF DIFFICULTY Moderate. The experiments require some experience in the handling of flies and in the preparation of microscope slides with fly wings. The original technique of mitotic recombination clones requires the availability of an X-ray source, which is the greatest restriction for this exercise.

INTRODUCTION

Vertebrate and invertebrate appendages have been used as model systems to study the mechanisms that underlie pattern formation in multicellular organisms. Experimental embryologists addressed these studies by microsurgical analysis (grafting, cauterization, etc.). Drosophila offers the advantage of a genetic system in which to decipher the roles of specific genes. Many genes have been identified and characterized that are involved in patterning Drosophila appendages. One of the most striking discoveries was the identification of “developmental compartments” (García-Bellido et al., 1973). Compartments were first identified in Drosophila as developmental restrictions detected by cell lineage analysis. These restrictions subdivide the wing into four different compartments: anterior (A), posterior (P), dorsal (D) and ventral (V) (Figure 14.1). The A/P restriction is established during early embryonic development and the D/V restriction is established during larval development (60 hours after egg laying (AEL)).