Analysis of Chromatin Structure and Composition.

Introduction Biochemistry, like many other sciences, is currently undergoing increasing specialization which is thought to be unavoidable because of the rapid progress within this field. Obviously education in Biochemistry and Molecular Biology is also affected. Consequently, the student may lose the ability to integrate his knowledge, which should be a requirement during the training of a scientist. The solution to this problem is quite easy in the case of theoretical courses because, here, the lecturer may include several 'integrative lessons' which give a global view of previously explained facts and place them within the general context of the course. However, in practical courses it is much more difficult to find solutions to the specialization problem. Practical courses are more suitable for focusing attention on a particular technique or problem and, moreover, most laboratories are highly specialized both in equipment and human resources. A feasible solution may be the elaboration of several short practical experiments one or two sessions that offer several special features. The experiments should be based in updated topics, they should have attractive and interpretable results and use unspecialized, lowcost equipment, ie available to every laboratory, and at the same time being versatile for providing different practical experiences. Finally, the experimental approaches used should be as varied as possible. Recently we have proposed a practical experiment that combines many of these features.l In it the student is initiated into the current techniques of recombinant DNA in prokaryotes. We now suggest a new experiment, along the same lines, whose aim is to study the genetic material of eukaryotes thus providing an appropriate complement to the preceding experiment. For this reason and because basically both experiments make use of the same equipment, they may be carried out together in four or five sessions. The experiment we propose completes and updates an experiment published in this journal several years ago. e This new experiment is based on the rapid growth and interest of the chromatin research over 1000 papers per year in international journals-making it of great interest for students of Biochemistry or Molecular Biology in any university curriculum. The material used, chicken erythrocytes, is easily obtained and has a simple chromatin organization due to its low metabolic activity. This simplicity facilitates the study of the chromatin because, although it has a typical nucleosomal structure, it is easier to obtain and study than the chromatin from other more active cells. 3 When the experiment is completed the student will have performed an almost comprehensive study of a defined material, the chromatin, by using several different experimental approaches.