July 14, 2021
In this IBDP Biology blog post, we will be looking at the key points when explaining the process of Meiosis, let's go!
Meiosis:
- Production of gametes: sex cells (have half as many chromosomes as other cells)
- separates sister chromatids + homologous chromosomeshomologous pairs are separated during meiosis I
- sister chromatids are separated during meiosis II
Before meiosis I, the cell goes through interphase: grows during G1, copies chromosomes during S phase, prepares for division during G2.
Meiosis 1:
Reduction division (diploid to haploid) in which homologous chromosomes are separated.
Prophase 1:
- chromosomes condense/ supercoil and pair up with their homologous partner
- homologous partners exchange part of their DNA thanks to the process of crossing over
Metaphase 1:
- homologous chromosomes line up in the middle of the cell - the metaphase plate/the equator of the cell thanks to the spindle fibresthe
- orientation of the chromosomes is random
Anaphase 1:
- homologous chromosomes are pulled apart towards the poles of the cell (the direction of each chromosome is random)
- sister chromatids remain together
Telophase 1:
- chromosomes arrive at cell poles
- the nuclear membrane may or may not reform cytokinesisoccurs at the same time as telophase 1
(forms 2 haploid daughter cells)
Meiosis 2:
The second division separates sister chromatids (chromatids may not be identical due to crossing over)
Prophase 2:
- chromosomes condense/supercoili nuclear membrane reformed in telophase 1, it breaks down
- centrosomes move to opposite poles
Metaphase 2:
- Spindles from opposing centrosomes attach to chromosomes at the centromeres
- They align them at the equator of the cell
Anaphase 2:
- Spindles contract and separate sister chromatids
- chromatids/chromosomes move to opposite poles
Telophase 2:
- chromosomes de-condensenuclear membrane reforms
- cells divide (cytokinesis) and form 4 haploid daughter cells
That is all you need to know for Meiosis, well done!
Drafted by Venetia (Biology)