The apterous gene in Drosophila encodes a protein required for wing patterning and growth. It is also known to function in nerve development, fertility, and viability. When human and mouse genes whose protein products closely resemble apterous were used to generate transgenic Drosophila (RinconLimas et al. \(1999 .\) Proc. Nat. Acad. Sci. \([\mathrm{USA}] 96: 2165-2170\) ) the apterous mutant phenotype was rescued. In addition, the whole-body expression patterns in the transgenic Drosophila were similar to normal apterous. (a) What is meant by the term rescued in this context? (b) What do these results indicate about the molecular nature of development?

The term "rescued" in this context refers to the restoration of the normal phenotype in the apterous mutant Drosophila, using the human and mouse genes encoding proteins similar to apterous. The fact that the mutant phenotype was rescued indicates that the human and mouse genes were able to replace the function of the mutated Drosophila apterous gene and contribute to the normal development of the organisms.

The results of the experiment indicate that the molecular nature of development shares a high level of conservation across different species, such as humans, mice, and Drosophila. This conservation is demonstrated by the fact that human and mouse genes were able to rescue the apterous mutant phenotype in Drosophila, restoring normal development. Additionally, the whole-body expression patterns in the transgenic Drosophila were similar to those of normal apterous, suggesting that these genes from different species have similar functions and are involved in the same developmental processes. This finding also implies that the underlying mechanisms of development, such as gene regulation, protein-protein interactions, and signaling pathways, are highly conserved across different organisms.