Yeast protein map showing relationships between proteins in the yeast Saccharomyces cerevisiae. Each dot represents one of the proteins found in this single-celled fungus. Lines link proteins that interact with each other. Proteins are colour-coded by the effect their removal has on the yeast: removal of red proteins was lethal, green was not lethal, orange caused slower growth and yellow had unknown effects. The proteins were removed by removing the gene that coded for their production. The more highly-connected proteins are more important for life. Work done by Jeong et al, at the University of Notre Dame, Indiana, USA.