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Metaphase (from Ancient Greek μετα- beyond, above, transcending and from Ancient Greek φάσις (phásis) 'appearance') is a stage of mitosis in the eukaryotic cell cycle in which chromosomes are at their second-most condensed and coiled stage (they are at their most condensed in anaphase). [1]
Chromosomes congress toward the metaphase plate of the cell. Metaphase: In this stage the chromosomes line up across the center of the cell and become connected to the spindle fiber at their centromere. Anaphase: In this stage the sister chromatids separate into individual chromosomes and are pulled apart.
Micrograph showing condensed chromosomes in blue, kinetochores in pink, and microtubules in green during metaphase of mitosis. In cell biology, the spindle apparatus is the cytoskeletal structure of eukaryotic cells that forms during cell division to separate sister chromatids between daughter cells.
Metaphase cells with low CENP-E levels by RNAi, showing chromosomes unaligned at the metaphase plate (arrows). These chromosomes are labeled with antibodies against the mitotic checkpoint proteins Mad1/Mad2. Hec1 and CENP-B label the centromeric region (the kinetochore), and DAPI is a specific stain for DNA.
Diagram of a duplicated and condensed eukaryotic chromosome. (1) Chromatid – one of the two identical parts of the chromosome after S phase. (2) Centromere – the point where the two chromatids touch, and where the microtubules attach. (3) Short arm (p). (4) Long arm (q).
Crossing over occurs between prophase I and metaphase I and is the process where two homologous non-sister chromatids pair up with each other and exchange different segments of genetic material to form two recombinant chromosome sister chromatids. It can also happen during mitotic division, [1] which may result in loss of heterozygosity.
It is now believed that this complex is mostly released from chromosome arms during prophase, so that by the time the chromosomes line up at the mid-plane of the mitotic spindle (also known as the metaphase plate), the last place where they are linked with one another is in the chromatin in and around the centromere.
Image of the mitotic spindle in a human cell showing microtubules in green, chromosomes (DNA) in blue, and kinetochores in red. [citation needed] Cells are broadly classified into two main categories: simple non-nucleated prokaryotic cells and complex nucleated eukaryotic cells. Due to their structural differences, eukaryotic and prokaryotic ...