How Body Cells How Body Cells ReproduceReproduceThe Cell CycleThe Cell Cycle

MitosisMitosis

The Cell CycleThe Cell Cycle

This is a continuous cycle of growth and division.

2 Phases:

-Growth (Interphase)

-Division (Mitosis)

InterphaseInterphase(Growth)(Growth)

This is the growth phase in which cells This is the growth phase in which cells make new molecules to increase its make new molecules to increase its volume and mass. volume and mass.

The cell is constantly synthesizing RNA The cell is constantly synthesizing RNA and producing protein. and producing protein.

This lasts anywhere from 12-24 hours.This lasts anywhere from 12-24 hours. Further divided into G1, S and G2 Further divided into G1, S and G2

phase.phase.

Phases of Phases of InterphaseInterphase

G1:G1: Gap 1, period of rapid growth and Gap 1, period of rapid growth and metabolic activity.metabolic activity.

S :S : Synthesis phase, DNA synthesis and Synthesis phase, DNA synthesis and ReplicationReplication

G2:G2: Gap 2, centrioles replicate and cell Gap 2, centrioles replicate and cell prepares for cell division.prepares for cell division.

Go:Go: There are times when a cell will leave the There are times when a cell will leave the cycle and quit dividing. This may be a cycle and quit dividing. This may be a

temporary resting period or more temporary resting period or more permanent. permanent.

MitosisMitosis(Division)(Division)

Shortest part of the cell cycle.Shortest part of the cell cycle. Occurs in all somatic (body) cells.Occurs in all somatic (body) cells. What is the Purpose?What is the Purpose?

- Growth- Growth

- Repair damaged tissues- Repair damaged tissues

- Replace old or damaged - Replace old or damaged cellscells

MitosisMitosis

One cell divides to produce 2 identical One cell divides to produce 2 identical daughter cells with the exact same number of daughter cells with the exact same number of chromosomes as the parent cell.chromosomes as the parent cell.

There are four phases:There are four phases:- Prophase- Prophase

- Metaphase- Metaphase

- Anaphase- Anaphase

- Telophase- Telophase

ProphaseProphase

Chromatin Chromatin (DNA and Protein)(DNA and Protein) condenses condenses and thickens to form visible and thickens to form visible chromosomes.chromosomes.

Each X shaped chromosome contains Each X shaped chromosome contains 2 copies of the original chromosome.2 copies of the original chromosome.

Each copy is called a chromatid.Each copy is called a chromatid. While they are attached, they are While they are attached, they are

considered to be ONE chromosome.considered to be ONE chromosome.

ProphaseProphase

Nuclear membrane and nucleolus Nuclear membrane and nucleolus disappear.disappear.

Centrioles migrate to opposite poles.Centrioles migrate to opposite poles. Spindle fibres form between the two Spindle fibres form between the two

centrioles.centrioles.

MetaphaseMetaphase

Spindle fibers attached to centromere Spindle fibers attached to centromere (where the two chromatids are attached)(where the two chromatids are attached) of of replicated chromosomes.replicated chromosomes.

Chromosomes line up in the middle of Chromosomes line up in the middle of cell also known as the equator.cell also known as the equator.

AnaphaseAnaphase

Centromere splitsCentromere splits Chromatids are pulled to opposite poles Chromatids are pulled to opposite poles

of the cell.of the cell.

TelophaseTelophase

The chromatids have now reached the The chromatids have now reached the opposite poles of the cell. opposite poles of the cell.

Each chromotid is now called a Each chromotid is now called a chromosome.chromosome.

Chromosomes unwind and become less Chromosomes unwind and become less visible.visible.

CytokinesisCytokinesis (Actual cell division)(Actual cell division)

Cytoplasm separates and a new cell Cytoplasm separates and a new cell membrane or cell wall is formed to create two membrane or cell wall is formed to create two new daughter cells. new daughter cells.

Nucleolus and nuclear membrane reappear.Nucleolus and nuclear membrane reappear.

QuestionsQuestions

Do all cells go through the cell cycle at Do all cells go through the cell cycle at the same rate?the same rate?

What would happen if the chromosomes What would happen if the chromosomes did not duplicate during interphase?did not duplicate during interphase?

Do sex cells go through mitosis?Do sex cells go through mitosis?

Error in MitosisError in Mitosis(Mutations)(Mutations)

Mutagens such as toxic compounds, Mutagens such as toxic compounds, radiation or viruses can cause mutations.radiation or viruses can cause mutations.

Mutations cause a permanent error or Mutations cause a permanent error or change in the normal DNA molecule that change in the normal DNA molecule that can be passed on to daughter cells can be passed on to daughter cells during anaphase.during anaphase.

Usually found in a localized group of Usually found in a localized group of cells.cells.

ExamplesExamples

If the FHIT gene which is located on If the FHIT gene which is located on chromosome #3 is mutated, it causes lung chromosome #3 is mutated, it causes lung cells to undergo mitosis more frequently and cells to undergo mitosis more frequently and results in a tumour.results in a tumour.

Oncogenes are genes that can be activated Oncogenes are genes that can be activated by a mutation and effect the cells rate of by a mutation and effect the cells rate of mitosis. mitosis.

If cells divide uncontrollably and rapidly, If cells divide uncontrollably and rapidly, tumours can develop and these tumours may tumours can develop and these tumours may become cancerous.become cancerous.

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