Fine Structure of Chromosomes

Abstract

Light microscopic studies of chromosomes since the time of the discovery of mitosis in 1878 have shown that the chromosomes of practically all eukaryotic species look very similar. It is therefore widely assumed, and in fact it has been shown for a great number of different and quite unrelated species, that the finer structural elements of chromosomes as well as their morphological organisation are similar. Despite the fact that this uniformity allows the study of the most favorable species our knowledge of the fine structure of chromosomes is still incomplete. One major reason for this is certainly the problem of artefacts, which arise with every sort of electron microscopic investigation. From ultrathin sections, the method which creates probably the least amount of artefacts, it is very hard to construct three dimensional pictures because of the very small size of the structural elements found in chromosomes. On the other hand, the methods of preparing chromosomes in toto are all connected with rather crude procedures causing many artefacts.