Chromosome

Abstract: Ohno and Hauschka1 showed that in female mice one chromosome of mammary carcinoma cells and of normal diploid cells of the ovary, mammary gland and liver was heteropyknotic. They interpreted this chromosome as an X-chromosome and suggested that the so-called sex chromatin was composed of one heteropyknotic X-chromosome. They left open the question whether the heteropyknosis was shown by the paternal X-chromosome only, or the chromosome from either parent indifferently.

Abstract: We describe an approach to detect the frequency of interaction between any two genomic loci. Generation of a matrix of interaction frequencies between sites on the same or different chromosomes reveals their relative spatial disposition and provides information about the physical properties of the chromatin fiber. This methodology can be applied to the spatial organization of entire genomes in organisms from bacteria to human. Using the yeast Saccharomyces cerevisiae, we could confirm known qualitative features of chromosome organization within the nucleus and dynamic changes in that organization during meiosis. We also analyzed yeast chromosome III at the G1 stage of the cell cycle. We found that chromatin is highly flexible throughout. Furthermore, functionally distinct AT- and GC-rich domains were found to exhibit different conformations, and a population-average 3D model of chromosome III could be determined. Chromosome III emerges as a contorted ring.

Abstract: This report describes the use of fluorescence in situ hybridization for chromosome classification and detection of chromosome aberrations. Biotin-labeled DNA was hybridized to target chromosomes and subsequently rendered fluorescent by successive treatments with fluorescein-labeled avidin and biotinylated anti-avidin antibody. Human chromosomes in human-hamster hybrid cell lines were intensely and uniformly stained in metaphase spreads and interphase nuclei when human genomic DNA was used as a probe. Interspecies translocations were detected easily at metaphase. The human-specific fluorescence intensity from cell nuclei and chromosomes was proportional to the amount of target human DNA. Human Y chromosomes were fluorescently stained in metaphase and interphase nuclei by using a 0.8-kilobase DNA probe specific for the Y chromosome. Cells from males were 40 times brighter than those from females. Both Y chromosomal domains were visible in most interphase nuclei of XYY amniocytes. Human 28S ribosomal RNA genes on metaphase chromosomes were distinctly stained by using a 1.5-kilobase DNA probe.

Abstract: Genes. Chromosomes: Deficiencies. Duplications. Inversions. Rings. Translocations. Transpositions. External Anatomy (figure). Normal Chromosome Complement. Special Chromosomes: Balancers. Compound Chromosomes. X-Y Combinations. Y Derivatives. Autosynaptic Chromosomes. Transposable Elements. Departures from Diploidy. Satellite Sequences. Nonchromosomal Inheritance. Cytogenetic Map.

Abstract: The male-specific region of the Y chromosome, the MSY, differentiates the sexes and comprises 95% of the chromosome's length. Here, we report that the MSY is a mosaic of heterochromatic sequences and three classes of euchromatic sequences: X-transposed, X-degenerate and ampliconic. These classes contain all 156 known transcription units, which include 78 protein-coding genes that collectively encode 27 distinct proteins. The X-transposed sequences exhibit 99% identity to the X chromosome. The X-degenerate sequences are remnants of ancient autosomes from which the modern X and Y chromosomes evolved. The ampliconic class includes large regions (about 30% of the MSY euchromatin) where sequence pairs show greater than 99.9% identity, which is maintained by frequent gene conversion (non-reciprocal transfer). The most prominent features here are eight massive palindromes, at least six of which contain testis genes.