These are the first eukaryotes to be used by genetic engineers:

Explanation

Answer is "Yeast"Explanation: Various yeast species have been genetically engineered to produce various drugs; Saccharomyces cervisiae is a simple eukaryotic cell, serving as a model for all eukaryotes. It is easy to genetically engineer. Its physiology, metabolism and genetics are amendable for use in harsh industrial conditions. A wide variety of chemicals of different classes can be produced by engineered yeast, including phenolics, isoprenoids, alkaloids and polyketides. About 20% biopharmaceuticals are produced by Saccharomyces cervisiae, including insulin, vaccine for hepatitis and human serum albumin.