Karyological Studies in Saccharomyces cerevisiae

Abstract

1. The nucleus of the vegetative cells of Saccharomyces cerevisiae is composed of a central deeply stained large karyosome, with a narrow hyaline zone around it, and an external membrane. The form of the karyosome is generally spherical, but sometimes it is irregular. It sometimes showed a granular structure in the case of treatment with ferments such as takadiastase. Small granules are often found around the nucleus.
2. The nucleus and also some granules are stained by the Feulgen nucleal reaction.
3. The nucleus undergoes mitosis. The resting nucleus becomes transformed into thick threads which become 4 chromosomes. The latter divide in the atractosome (spindle) to form two daughter nuclei.
4. After mitosis one of the newly formed daughter nuclei, taking on a dumbbell shape, travels through the isthmus into the bud, while the other one remains in the mother cell as its nucleus.