Classtalk: A Classroom Communication System for Active Learning

This pdf file is an article describing the advantages of using Classtalk technology in the classroom to enhance classroom communication. Classtalk technology cab facilitate the presentation of questions for small group work, collec the student answers and then display histograms showing how the class answered. This new communication technology can help instructors create a more interactive, student centered classroom, especially when teaching large courses. The article describes Classtalk as a very useful tool not only for engaging students in active learning, but also for enhancing the overall communication within the classroom. This article is a selection from the electronic Journal for Computing in Higher Education. Educational levels: Graduate or professional

Nonrandom inactivation of the Y-bearing X chromosome in a 46, XX individual: evidence for the etiology of 46, XX true hermaphroditism

We previously reported a subject with 46, XX true hermaphroditism who had a 46, X, del(X) karyotype and Y-chromosomal sequences in genomic DNA. We hypothesized that the Y-chromosomal sequences were translocated to the deleted X chromosome and that the incomplete testis determination of this individual was the result of inactivation of the translocated X chromosome. In situ hybridization studies demonstrated that the Y-chromosomal sequences were located on the distal portion of the short arm of the deleted X chromosome. Investigation of the replication of the X chromosome, using a modified R-banding technique and localization of Y-chromosomal sequences by in situ hybridization, showed that the translocated X chromosome was late replicating in all 100 EBV-transformed lymphoblasts that were examined. By contrast, when cells from a subject with 46, XX maleness were studied, the translocated X chromosome was late replicating in only 21 of 47 cells. As the late-replicating X chromosome is presumed to be the inactive X chromosome, selection of cells in which the Y-bearing X chromosome has been inactivated may play a role in the incomplete testis determination in subjects with “Y-positive” 46, XX true hermaphroditism