Metaphase

Content
Physical Basis of Heredity 2.  Cell Division (Mitosis and Meiosis)
Mitosis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Meiosis 
Significance of meiosis
Reproductive cycles
Stages of meiosis
Synaptonemal complex
Recombination nodules
Comparison of meiosis and mitosis


At late prophase or early metaphase, spindle tubules start appearing. These tubules get attached to chromosomes at centromeres. The chromosomes begin active movement leading to arrangement of chromosomes in the centre or at equatorial plate. The spindle apparatus, which helps in arrangement of chromosomes at the plate, is formed with the help of centrosome particularly in case of animal cells. Centrosome has two centrioles which separate at the time of spindle formation and occupy positions on opposite sides of nucleus. As two centrioles separate, astral rays appear radiating outward from each centriole. These will join and form spindle fibres. In most plants, centrosomes are missing, but spindle apparatus is still formed. Mechanism of its formation is discussed in the next main topic.
 
Various stages of mitosis in a somatic cell.
Fig. 7.3. Various stages of mitosis in a somatic cell.