Metaphase
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Metaphase (from the Greek words μετά = after and φάσις = stage) is a stage of mitosis in the eukaryotic cell cycle in which condensed chromosomes align in the middle of the cell before being separated into each of the two daughter cells.
One of the cell cycle "checkpoints" occurs during metaphase. Only after all chromosomes have become aligned at the metaphase plate does the cell enter anaphase. This is accomplished by regulation of the APC, securin, and separase. Metaphase is preceded by prophase and followed by anaphase.
The analysis of metaphase chromosomes is one of the main tools of cancer cytogenetics. Malignant cells from solid tumors or leukemia samples are grown in short term culture and dropped onto microscope slides to generate metaphase preparations. Staining of the slides (Giemsa, Quinacrine) produces a pattern of in total up to several hundred bands. Inspection of the stained metaphases allows the determination of numerical and structural changes in the tumor cell genome, e.g. losses of chromosomal segments or translocations, which may lead to chimeric oncogenes (e.g. bcr-abl in Chronic myelogenous leukemia).
Additionally, normal Metaphase spreads are used as hybridization matrix for Comparative Genomic Hybridization (CGH) experiments.