This paper deals with a flowshop scheduling problem with a special blocking RCb (Release when Completing Blocking). In some industrial environments, such flexible production systems can be encountered. Genetic algorithms are good methods to solve these problems. A method is proposed to further improve solutions already found by genetic algorithms. It consists in marking out recurrent genes association occurrences in an available already optimized population. Main directing idea follows Holland’s statements observing that a problem good adapted population has an adapted genetic code with some common properties. Marking out common properties in a population improves genetic algorithm efficiency. Implementation of this method is presented and obtained results on flowshop scheduling problems are discussed.