The sequence of many eukaryotic genomes is nowadays available from a personal computer to any researcher in the world-wide scientific community. However, the sequences are worthless without the adequate annotation of the biological meaningful elements. The annotation of the genes, in particular, is a challenging task that can not be tackled without the aid of specific bioinformatics tools. We present in this chapter a simple protocol mainly based on the combination of the program GeneID and other computational tools to annotate the location of a gene, which was previously annotated in D. melanogaster, in the recently assembled genome of D. yakuba.