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Cell Cycle and Mitosis

Cell Life Span and Reproduction

Question of the Day?How do cells reproduce?

Cell Cycle of a Somatic Cell

• 1. G 1 – Growth; Cell matures and spends most of its life. • 2. S-Phase – DNA Replication occurs • 3. G 2 – Cells continues to grow and prepares for division • 4. M – Phase – Cell Divides • 5. Interphase – G1 , S-Phase, and G2. Cells spends most of its life.

M – Phase(Mitotic Phase)Where the cells divides. •Divided into several sections:

Prophase Metaphase Anaphase TelophaseCytokinesis

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A. Motor ProteinsB. SpindlesC. CentriolesD. KinetochoresE. Histones

2. Label Each Stage of Mitosis Below:1. The region which spindle fibers

connect to sister chromatids are known as:

Cell Cycle and ErrorsAP BIOLOGY 12.3

The Cell Cycle Control System• Cell Cycle Control System – operating set of molecules in the cell that

triggers and coordinates events within the cell cycle.• Within the cell cycle there are checkpoints which serves as a stop and

go signal.• Signals are controlled by cellular surveillance mechanisms inside the cell

• Are crucial steps done correctly? If not, cell cycle will not continue.• There are three major checkpoints found in the G1, G2, AND M phases.

Importance of the G1 Stage• G1 phase is considered the “restriction point” in mammalian cells• If a cell receives the go-ahead signal it will complete all the stages and

divide after mitosis.• If a cell does not receive the go – ahead the cell will go into the𝐺0 phase where the cell will not divide.• Example – nerve and muscle cells• In some cases – liver cells can be “called back” by external cues in order to

repair an injury.

The Cell Cycle Clock

• Regulatory mechanisms are controlled by proteins• Two types – kinases and cyclin

• Kinases protein is responsible for driving the cell cycle but are often found inactive.• Kinases attaches to cyclin to become active : cyclin-dependent

kinases, or Cdks.• MPF (m-phase promoting factor) triggers the cells passage past the

G2 checkpoint.

Error in the Cell Cycle in CancerCells

• Cancer cells divide excessively and do not follow normal signals which regulate the cell cycle.• Invade other tissues

• Caner cells do not exhibit density-dependent inhibition• Phenomenon which overcrowded cells stop dividing

• Cancer can become dangerous when nearby tissue undergoesTransformation.• Cancer cells convert normal cells into cancer cells

• The body normally destroys cancer cells, but sometimes cells are not destroyed and forms tumors

Types of Tumors• Benign – tumors which are

non-cancerous and can be removed surgically

• Malignant – cells that can become invasive enough to impair the functions of one or more organs.

• Cancerous Cells• Send signals to cause blood

vessels to grow towards the tumor (nutrients)

• Can spread to other areas of the body – Msetastasis

Treatment ofTumors• Localized tumors can be

treated with high amounts ofradiation

• Damages DNA and cancerous cell lost the ability to correct this action.

• Metastatic cells are treated with chemotherapy; targets actively dividing cells by disrupting metaphase (Taxol). Without metaphase the cell cannotdivide.• Also effects intestinal and

hair cells.

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