A method for nucleic acid hybridization to isolated chromosomes in suspension

A procedure was developed to provide differential fluorescent staining of metaphase chromosomes in suspension following nucleic acid hybridization. For this purpose metaphase chromosomes were isolated from a Chinese hamster x human hybrid cell line. After hybridization with biotinylated human genomic DNA, the human chromosomes were visualized by indirect immunofluorescence using antibodies against biotin and fluoresceine-isothiocyanate-(FITC)-labeled second antibodies. This resulted in green fluorescent human chromosomes. In contrast, Chinese hamster chromosomes revealed red fluorescent staining only when counterstained with propidium iodide. Notably, interspecies chromosomal rearrangements could be easily detected. After hybridization and fluorescent staining, chromosomes still showed a well-preserved morphology under the light microscope. We suggest that this procedure may have a useful application in flow cytometry and sorting

Sorting of chromosomes by magnetic separation

Chromosomes were isolated from Chinese hamster x human hybrid cell lines containing four and nine human chromosomes. Human genomic DNA was biotinylated by nick translation and used to label the human chromosomes by in situ hybridization in suspension. Streptavidin was covalently coupled to the surface of magnetic beads and these were incubated with the hybridized chromosomes. The human chromosomes were bound to the magnetic beads through the strong biotin-streptavidin complex and then rapidly separated from nonlabeled Chinese hamster chromosomes by a simple permanent magnet. The hybridization was visualized by additional binding of avidin-FITC (fluorescein) to the unoccupied biotinylated human DNA bound to the human chromosomes. After magnetic separation, up to 98% of the individual chromosomes attached to magnetic beads were classified as human chromosomes by fluorescence microscopy

Descriptions of three new species of Melanochromis (Teleostei: Cichlidae) and a redescription of M. vermivorus

The Lake Malaŵi genus Melanochromis included five species at its inception and was originally distinguished from Pseudotropheus on the basis of morphology including the arrangement of pharyngeal teeth. The diagnosis has been extended twice, first to include all elongate mbuna that possess horizontal stripes and U-shaped tooth bands and later to exclude mbuna that do not exhibit a sex-related reversal in their color pattern. We have further refined the diagnosis of the genus on the basis of the melanin pattern, resolved a longstanding dispute regarding the validity of M. heterochromis, re-evaluated the status of M. vermivorus, synonymized M. mellitus Johnson 1976 with M. melanopterus Trewavas 1935, moved M. benetos Bowers and Stauffer 1977 to Pseudotropheus, and described M. kaskazini, M. wochepa, and M. mossambiquensis from the eastern shore of the lake. Melanochromis is still paraphyletic as two species, M. joanjohnsonae Johnson 1974 and M. labrosus Trewavas 1935, are not congruent with the rest of the group, but, currently, a better alternative for these two could not be found.</jats:p