Metaphase: Metaphase is a stage during the process of cell division (mitosis or meiosis). Normally, individual chromosomes are spread out in the cell nucleus. During metaphase, the nucleus dissolves and the cell’s chromosomes condense and move together, aligning in the center of the dividing cell. At this stage, the chromosomes are distinguishable when viewed through a microscope. Metaphase chromosomes are used in karyotyping, a laboratory technique for identifying chromosomal abnormalities.
Key features of Metaphase
- Chromosomes are completely condensed and can be seen under the microscope.
- The nuclear envelope disintegrates completely and chromosomes are present in the cytoplasm.
- Sister chromatids are attached to each other at centromere by a protein complex called cohesin.
- Microtubules bind to the kinetochore of sister chromatids. The kinetochore is a multiprotein complex attached to each centromere.
- Sister chromatids get attached to kinetochore microtubules coming from opposite poles.
- Microtubules attached to kinetochore pull sister chromatids back and forth until they get aligned at the equatorial plate or metaphase plate in the middle of the cell.
- Metaphase ensures an equal division of chromosomes in the daughter cells.
- Karyotyping is generally done at this stage for research and finding chromosomal abnormalities.
- Colchicine, an alkaloid derived from the corm of Colchicum autumnale, arrests cell division at metaphase. It interferes with the formation of spindle fibres.
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