In this module, students prepare extracts from Saccharomyces cerevisiae strains that have been transformed with expression plasmids. Expression from the plasmids is controlled by the inducible GAL1 promoter. Cell extracts are analyzed by protein electrophoresis in other modules. At the end of this module, students will be able to:compare the effects of different carbon sources on transcription of gene controlled by the yeast GAL1 promoter.explain the roles of heat and detergents in the preparation of yeast cell extracts.prepare extracts from transformed yeast strains suitable for analysis by SDS-PAGE gels and western blots.This module is part of a semester-long introductory laboratory course, Investigations in Molecular Cell Biology, at Boston College.