Evaluation of electronic discussion groups as a teaching/learning strategy in an evidence-based medicine course: a pilot study.

Background: As course directors, we wished to incorporate small group learning into our Evidence-based Medicine course for students to get feedback on the development of a well constructed, researchable clinical question. Scheduling of these groups was problematic. We sought to evaluate computer-mediated communication as an alternative to face-to-face small groups.

Molecular analysis of X chromosome dosage compensation in Caenorhabditis elegans.

We used a convenient quantitative dot blot assay to measure transcript levels for two X chromosome-linked genes, myo-2 and act-4, in the nematode Caenorhabditis elegans. We show that there is dosage compensation of transcript levels for these two genes between XX hermaphrodites and X0 males and that a mutation in the dpy-21 gene, postulated from genetic analysis to be involved in control of X chromosome expression, can affect these transcript levels in the manner predicted. However, we observe the dpy-21 effects only at some stages of the life cycle and not at others.

Electrophoretic variation for X chromosome-linked hypoxanthine phosphoribosyl transferase (HPRT) in wild-derived mice.

An electrophoretic variation for hypoxanthine phosphoribosyltransferase, HPRT, has been identified in samples of Mus spretus, a field mouse from southern Europe and in M. m. castaneus, a house mouse from southeast Asia.

Evidence for DNA modification in the maintenance of X-chromosome inactivation of adult mouse tissues.

The role of DNA modification in the maintenance of mammalian X-chromosome inactivation was investigated by using the technique of DNA transformation in mammalian cells. The ability of inactive X-chromosome DNA from adult mouse tissues to act in transformation for the X-linked hypoxanthine phosphoribosyltransferase gene (Hprt) could be ascertained by utilizing a recently discovered electrophoretic variant form of the hypoxanthine phosphoribosyltransferase enzyme and a previously available X:autosome translocation. Our findings indicate that inactive X-chromosome DNA from several tissues of adult female mice is strikingly inefficient, in comparison to active X-chromosome DNA, in eliciting genetic transformation for hypoxanthine phosphoribosyltransferase.