Biology GCSE (1)

Growth

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Growth!

Two methods of cell division - Mitosis, meiosis!

Cell ---> nucleus with chromosomes in ---> DNA doubles ---> Nucleus disappears and fibre forms ---> fibre pulls chromosomes apart ---> Chromosomes have been sepparated and nucleus reforms to produce two genetically identical cells.

Mitosis is responsible for - Growth, Replacement & Repair.

ASEXUAL REPRODUCTION!

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Mitosis

Mitosis in animals - 

  • all tissues in the body will undergo mitosis at some stage in their development.
  • Some of these tissues are more efficient at this type of cell division e.g. skin cells - have a special layer of that keeps replacing cells that wear away throughout your life.
  • Red cells are produced in the bone marrow - mature red blood cells don't posses a nucleus, they had a nucleus at the early stage of development.
  • Nerve cells - aren't very good at replacing themselves.
  • Animals are able to repair most damaged tissues using mitosis.
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Mitosis in plants

  • the parts that undergo mitosis are limited to the growing areas.
  • Meristems - regions of the plant where growth due to mitosis occurs/responsible for the growth of the roots downwards into the soil and upwards towards light.
  • tips of roots and the shoots there are areas of growth to which mitosis is confined.
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