- Meiosis- It is a reduction division. This means that the daughter cells have half of the original number of chromosomes. They are haploid.
- Each division has four stages:
- Before meiois 1, interphase takes place. This is when the DNA replicates. Each chromosome consists of two identical chromatids, joined at the centromere.
- The cell will have four instead of two original copies of each chromosme.
- Each chromosome is a chromatid.
- A pair is called a sister chromatid.
- Sister chromatids are joined together in the middle by a centromere.
- The chromatins condenses and supercoils.
- Supercoiling makes the chromosomes shorter and thicker.
- The chromosomes come together as homologous pairs to form a bivalent.
- A bivalent is a pair of homologous chromosomes.
- Each member of the pair have the same gene at the same loci. They each have the one maternal and one paternal chromosome.
- Non sister chromatids wrap around each other and form chiasmata.
- The undergo a process called crossing over. This is when the chiasmata may swap section s of chromatid with one another.
- The nucleolous disappears and the nuclear envelope breaks down.
- A spindle is formed. It is made of protein microtubles.
- The bivalent line across the equator of the cell and they attach to spindle fibres at the centromere.
- Each member of the homologous pairing face opposite poles.
- The homologous chromosome pair are pulled to opposite end of the poles.
- This is because the spindles contract pulling them apart.
- There is two nuclear envelope that forms around the chromosomes at each end of the poles.
- In animals, the cytoplasm divides by cytokenesis and two haploid daughter cells are formed.
- In plants, the cell goes straight from anaphase 1 to meiosis 2.
- This is the same as meiosis one, however, it occurs with half the number of chromosomes.
- In anaphase 2, the sister chromatids are seperated. Each new daughter cell…