Cell division


L.O To understand the principles of mitosis and meiosis.

For organisms to survive, cell division has to occur, to ensure that the organism can grow and replace any lost cells.

There are two types of cell division,  mitosis and meiosis.

 

Mitosis


Mitosis is performed when a cell is required to produce two identical offspring. Cells usually have two copies of chromosomes within the nucleus.

Mitosis is the process of splitting one cells to produce two identical copies

Mitosis

Mitosis is primarily used in Asexual reproduction, this type of reproduction has no variation and is mainly used in plants and bacteria.

 

Meiosis


Meiosis produce cells which have half the number of chromosomes and are not exactly the same.
Meiosis only occurs in reproductive organs where the products have to be genetically different

Meiosis

Meiosis1

Meiosis2

X and Y chromosomes
In the human body we have 23 pairs of chromosomes, however the 23rd pair is responsible for our gender. It either comes in the form of XX or XY. XY determines a male and XX determines a female

Genetic diagrams show the possibility of what gender the gamete will be. As the sperm will be carrying an X and a Y, and the female egg cell will be carrying a X and a X.
When the sperm and egg fuse together there is a 50% chance of either combination forming as shown below

X and Y chromosomes

Shown above is a genetic diagram. The first set of genes are the parents and then they are split up in the next row to highlight the possible combinations, and in the final set those are the possible combinations of gametes. Note that only one of these combinations will actually happen.

 

 

 

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