Meiosis II – Class 12 | Chapter – 10 | Biology Short Notes Series PDF
Meiosis II is the second round of cell division in the process of meiosis or the creation of gametes (sex cells). Directly after meiosis I, the two haploid daughter cells with extra chromosome copies undergo meiosis II, so that the sister chromatids, or identical chromosome copies, can be split evenly to produce four haploid daughter cells. This means that after meiosis I the two daughter cells do not re-enter interphase and no duplication event occurs between meiosis I and meiosis II. Some cells may go through a brief period between these two parts of meiosis called interkinesis.
Stages of Meiosis II
The stages that make up meiosis II are the same as those in meiosis I and mitosis, except that they contain the roman numeral “II” after each stage. They are as follows:
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Prophase II
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Metaphase II
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Anaphase II
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Telophase II and cytokinesis.
Prophase II
During prophase II, as in mitosis and meiosis I, the following steps occur:
- Nuclear envelope begins to dissolve.
- Centrosomes (in animal cells) migrate to opposite poles of the cells.
- The chromosomes condense to prepare for movement to opposite poles of the cell.
- Spindle fibers begin to form.
Metaphase II
During metaphase II, the chromosomes align in a single line at the metaphase plate. In this stage of meiosis, the sister chromatids are preparing to be separated.
Anaphase II
During anaphase II the spindle fibers, connected at the kinetochores of each chromatid, pull the chromatids to opposite cell poles. The spindle fibers not connected to a chromatid help push the centrosomes of the opposite poles.
Telophase II and cytokinesis
During telophase II, the two cells are preparing to become four after the sister chromatids are separated in anaphase II and the genetic material corresponding to each cell is at opposite poles. In this stage of meiosis II, the chromosomes are decondensing as the nuclear envelope reforms, making the nuclei of the future independent cells. Spindle fibers break down and the centrosomes disassemble. Finally, in telophase II, the cleavage furrow (in animal cells) begins to form as the cells prepare for cytokinesis.
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