3.3 Meiosis
Understanding:
One diploid nucleus divides by meiosis to produce four haploid nuclei.
Meiosis in Outline:
Stages of Mitosis:
Prophase I:
Metaphase I:
Meiosis in Outline:
- one of the two ways in which the nucleus of a eukaryotic cell can divide (the other method is mitosis)
- the nucleus divides twice in meiosis (first division produces two nuclei, second division produces four nuclei, known as meiosis I and meiosis II)
- the nucleus that undergoes the first division of meiosis is diploid (two chromosomes of each type or homologous chromosomes)
- each of the four nuclei produced by meiosis has just one chromosome of each type - they are haploid
- Meiosis involves halving the chromosome number (therefore, known as reduction division)
- the two nuclei produced by meiosis I have the haploid number of chromosomes (but each chromosome still consisted of two chromatids)
- the four nuclei produced by meiosis II have the haploid number of chromosomes (but with each chromosome consisting of a single chromatid)
Stages of Mitosis:
Prophase I:
- Synapsis (homologous chromosome pair)
- Crossing over
Metaphase I:
- Random Orientation
- Spindle microtubules move homologous pairs to the equator of the cell