Tag Archives: Metaphase

Two Nuclei from one

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Whats so important about making newcells?

  • Asexual reproduction
  • Growth
  • Repair
  • Replacement

Mitosis

  • Mitosis refers to the process where nuclear division takes place and two new gentically identical nuclei form from one parent nucleas
  • This process is broken into seperate phases
  • Prophase
  • metaphase
  • Anaphase
  • Telophase

 

Prophase

  • The chromosomes supercoil and become visible under the light microscope
  • The Nuclear envelope breaks down and dissapears
  • The centriole divides into 2 and moves to seperate ends of the poles within the cells
  • The centrioles then form a spindle
  • The spindle is made of protein

Metaphase

  • The chromatids move to the equator and hang from the spindle via the centromere

Anaphase

  • The centromere splits
  • the chromatids are pulled apart
  • the now seperated chromosomes move towards opposite poles
  • they form a V shape as they move towards the poles as the Centromere is in the lead
  • The spindle fibres shorten, that is why they are pulled towards opposite poles

Telophase

  • As the seperated (Gentically identical) Chromosomes head towards their respective poles, a new nuclear envelope forms around each ste
  • the spindle breaks down and dissapears
  • The chromosomes uncoil so you can no longer see them under the light microscope

Cytokenisis is not considered to be a part of the Mitosis, however it is known as the cleavage of the cytoplasm.

 

As shown in the picture above, Mitosis (M) only occupies a small percentage of the actual cell cyle, Interphase is the phase that happens before Mitosis and consists of

  • G1: Biosynthesis, this means that proteins are made and organnelles are replicated
  • S is synthesis of new DNA, so basically the replication of chromosomes
  • and G2 is growth
  • Then it is over to Mitosis

 

  • There is a time and a place for the cell division to occcur, in animals, most cells are capable of mitosis and cytokenisis
  • However in plants, only special cells known as meristem cells can undergo cell division
  • Plant cells also do not have centrioles, the tubulin protein threads are made in the cytoplasm
  • In animal cells, cytokinesis starts from the outside
  • in plant cells, it starts with the formation of a cell plate, where the spindle equator was
  • new cell wall and membrane are laid down along this plate