IB DP Biology: HL复习笔记10.1.4 Meiosis II
Meiosis II
Second division of Meiosis : Meiosis II
- There is no interphase between meiosis I and meiosis II so the DNA is not replicated
- The second division of meiosis is almost identical to the stages of mitosis
- Prophase II
- The nuclear envelope breaks down and chromosomes condense
- A spindle forms at a right angle to the old one
- Metaphase II
- Chromosomes line up in a single file along the equator of the spindle
- Anaphase II
- Centromeres divide and individual chromatids are pulled to opposite poles
- Sister chromatids separate in meiosis (anaphase) II
- However, they are likely to be non-identical sister chromatids at this stage due to crossing over having happened in prophase I
- This creates four groups of chromosomes that have half the number of chromosomes compared to the original parent cell
- Telophase II
- Nuclear membranes form around each group of chromosomes
- Cytokinesis
- Cytoplasm divides as new cell surface membranes are formed creating four haploid cells
Prophase II, Metaphase II and Anaphase II in Meiosis II of an animal cell
Telophase II and cytokinesis in Meiosis II of an animal cell
Exam Tip
Because of the many similarities between mitosis and meiosis II, you are more likely to get a detailed question on meiosis I than meiosis II and the sources of variation that occur in meiosis I. Revise them both though!
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