T WAS recently found (NEBEL and RUTTLE, in press) that Tradescantia I reflexa Raf. shows four threads1 per chromosome during all somatic as well as during all premeiotic stages. Multiplication of threads occurs a t metaphase during somatic division (fig. I). In meiosis of T . reflexa the four threads multiply a t early interkinesis and do not do so again until the metaphase of the first pollen ...

X inactivation is a chromosome-specific form of genetic regulation in which thousands of genes on one homologue become silenced early in female embryogenesis. Although many aspects of X inactivation are now understood, the spread of the X inactivation signal along the entire length of the chromosome remains enigmatic. Extending the Gartler-Riggs model [Gartler, S. M. & Riggs, A. D. (1983) Annu....

X-chromosome inactivation is normally a random event that is regulated by the X chromosome itself. Rarely, females are affected by X-linked disorders from extremely skewed X-chromosome inactivation. Here, we report a family with hemophilia B with female expression through inherited X skewing that appears to be independent of either X chromosome. This finding suggests the possibility of a domina...