A polar filter in DNA polymerases prevents ribonucleotide incorporation.

The presence of ribonucleotides in DNA can lead to genomic instability and cellular lethality. To prevent adventitious rNTP incorporation, the majority of the DNA polymerases (dPols) possess a steric filter. The dPol named MsDpo4 (Mycobacterium smegmatis) naturally lacks this steric filter and hence is capable of rNTP addition.

Reflective practice: a framework for case manager development.

Purpose/objectives: The role of a nurse case manager (NCM) incorporates practice that is built upon knowledge gained in other roles as well as components unique to case management. The concept of reflective practice was used in creating a framework to recognize the developmental stages that occur within community based case management practice. The formation of this framework and its uses are described in this article.

Distribution of kinetochore fragments during mitosis with unreplicated genomes.

When hydroxyurea and caffeine are added to Chinese hamster ovary cells, the cells bypass the S-phase checkpoint, and enter unscheduled mitosis. These cells build a morphologically normal spindle, and distribute unreplicated kinetochore fragments to daughters. We examined these cells and found that they undergo a full repertoire of mitotic stages, with the exception of anaphase B.

Localization of spindle checkpoint proteins in cells undergoing mitosis with unreplicated genomes.

CHO cells can be arrested with hydoxyurea at the beginning of the DNA synthesis phase of the cell cycle. Subsequent treatment with the xanthine, caffeine, induces cells to bypass the S-phase checkpoint and enter unscheduled mitosis [Schlegel and Pardee,1986, Science 232:1264-1266]. These treated cells build a normal spindle and distribute kinetochores, unattached to chromosomes, to their daughter cells [Brinkley et al.