Mitosis Learning Objectives: State why cells divide Wednesday, 11 April 2018 Mitosis Learning Objectives: State why cells divide Describe the advantages of being multi-cellular Explain how cells divide by mitosis Starter Why do you need to make new cells?

Why do you need new cells Skin cells are continually lost. To make new cells the body carries out cell division Cells divide where the body needs to: Grow Replace worn out cells Repair damaged tissue

Difference between… Uni-cellular And Multi-cellular

Differentiation…recap Differentiation: Cells become different shapes of sizes to carry out specialised jobs

Advantages of being multi-cellular Can grow larger Differentiation means cells become specialised to perform different functions Become more complex eg develop organ systems.

Chromosomes recap Every cell contains 46 pairs of chromosomes. These pairs are said to be homologous A cell that has pairs of chromosomes is said to be diploid

Keywords Spindle- Structure in cells that separates the chromosomes during cell division. Diploid- Full set of chromosomes (46) Haploid- Half set of chromosomes (23) e.g. Sperm cell.

Mitosis The name for making new cells. The new cells are genetically identical to the original cell

Stages of mitosis Chromosome single strands move to the poles of the cell Spindle forms. Chromosomes arranged along the equator Each chromosome is copied (DNA replication) Cell resting Two genetically identical cells are produced Mitosis. Mitosis. What every cell knows is… it happens all the time.

Cells undergoing mitosis

A cell has 2 versions of each chromosome – one from each parent. We call this type of cell diploid.

To prepare for cell division, each chromosome is copied.

The chromosomes line up in the centre of the cell.

The two copies of each chromosome are pulled apart by spindle fibers.

The chromosomes move to different sides of the cell. Cytoplasm Divides. The cell begins to split in two.

The cell completely splits in two. There are now two cells, these are called daughter cells (both diploid). Each cell is genetically identical to each other, and to the original parent cell.

Asexual Reproduction Some organisms reproduce by mitosis. E.g. Strawberry plants form runners in this way which become new plants. This is an example of asexual reproduction. The offspring have exactly the same genes as the parent- therefore......

Where does mitosis happen? Most of the cells in the body divide by mitosis. Can you think of any exceptions? Some organisms can reproduce by mitosis. This is called asexual reproduction. Examples include yeast and the malaria parasite.

Cancer and Mitosis? Is there any link?

What happens when mitosis goes wrong? Usually cells only divide at certain times. Sometimes this control stops working and cells divide uncontrollably – this is cancer.

What is mitosis? Why is mitosis important? What would happen if mitosis didn’t take place? Suggest one advantage and one disadvantage of asexual reproduction. What is meant by a diploid cell? What cells in the body do you think are not diploid? How many parents does a cell that reproduces by sexual reproduction have? How many parents does a cell that reproduces by asexual reproduction have? Can you give an example of what happens when mitosis goes wrong?