In IBDP Biology, we are to know what is mitosis and meiosis, two very different processes. We will begin to learn what is Mitosis first, as well as the overall cell cycle within cellular organisms.

Cell Cycle

Within a cell cycle, there are 3 main stages, including interphase (G1, S, G2 aka largest phase), which then leads to mitosis and cytokinesis.

Interphase: An active period during which the cell carries out many biochemical reactions and grows larger.

• G1

: A period of growth, DNA transcription and protein synthesis

• S:

 The period during which all DNA in the nucleus is replicated.

• G2:

 Cell prepares for division. There are more organelles and DNA condenses into visible chromosomes.

Mitosis

Mitosis: Nucleus divides into two genetical nuclei, (Remember in IBDP Biology: PMAT!)

1. Prophase:

1. Spindle microtubules grows
2. Chromosomes are becoming smaller by 

supercoiling

1. Each chromosome consists of

 two identical chromatids formed by DNA replication held by centromere

1. 2.

 Metaphase:

1. The nuclear membrane has broken down and chromosomes have moved to the equator
2. Spindle microtubules from both poles are attached to each centromere, on opposite sides.

3. Anaphase:

1. The 

centromeres have divided and the chromatids have become chromosomes

1. Spindle microtubules pull the genetically identical chromosomes to 

opposite poles

4. Telophase:

1. All chromosomes have reached the poles and 

nuclear membranes form around them

1. Spindle microtubules break down
2. Chromosomes uncoil

 and are no long individually visible

Mitosis is used in eukaryote whenever genetically identical cells are needed eg. embryonic development, when the large cell produced by fertilization (zygote) divides repeatedly to produce many smaller cells; growth; to reproduce asexually

• Tumor

 (cancers) are the result of uncontrolled mitosis. The normal control of mitosis in a cell fails, due to a change in the genes of the cells. This can happen in any tissue or organ and can spread to any part of the body.

Cytokinesis

Within IBDP Biology, we are to know that animals and plants have different stages of cytokinesis (the process of dividing the cytoplasm to form two cells), for animals:

• A contractile ring composed of 
• actin filaments

 forms just inside the plasma membrane at the former metaphase plate. The actin filaments pull the equator of the cell inward, forming a cleavage furrow. It then separates the membrane into two

For plants:

• A cell plate forms along the equator of the parent cell during telophase from enzymes. Then, a new cell membrane and cell wall form along each side of the cell plate and waste is carried out through vesicles

That is the end of the cell cycle/ Mitosis!

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References:

https://labster-image-manager.s3.amazonaws.com/90358662-0e92-4f2f-9c92-4536ddcd81ba/MIL_MitosisGraph_1.en.x512.png

https://www.google.com/url?sa=i&url=https%3A%2F%2Ftenor.com%2Fsearch%2Fyay-gifs&psig=AOvVaw2ncmHKD0edvWfwP_aM23cW&ust=1624867872537000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCMDCntiut_ECFQAAAAAdAAAAABAD

Written by Venetia (Biology)