The Cell Cycle  Remember: When cells get to large they cannot get enough nutrients into and out of the cell.  Cell division prevents the cell from becoming too large.  Cell division is the way the cell reproduces so that you grow and heal certain injuries.  Cell division is asexual reproduction meaning the offspring are clones/identical to the parent. Cellular Reproduction Section 1 Cellular Growth

 Cells reproduce by a cycle of growing and dividing called the cell cycle.  The cell cycle includes the following 5 phases  Interphase 1.G1 (1 st growth phase) 2.S (Synthesis phase) 3.G2 (2 nd growth phase) 4.Mitosis 5.Cytokinesis Cellular Reproduction Section 1 Cellular Growth

 Interphase is the stage during which the cell grows, carries out cellular functions, and replicates.  Mitosis is the stage of the cell cycle during which the cell’s nucleus and nuclear material divide.  Cytokinesis is the method by which a cell’s cytoplasm divides, creating a new cell. Cellular Reproduction Section 1 Cellular Growth

Stages of Interphase

Cellular Reproduction The Stages of Interphase  G 1 - The first stage of interphase  The cell is growing  Carrying out normal cell functions Section 1

Cellular Reproduction  The cell copies its DNA in preparation for cell division. S – Synthesis Second Stage of Interphase Section 1

Cellular Reproduction G 2 Third Stage of Interphase  The cell prepares for the division of its nucleus. Section 1

Cellular Reproduction Mitosis  Mitosis is the division of the nucleus where the DNA is divided equally into two new nuclei.  During the S Phase of interphase, the DNA is copied Section 2

Cellular Reproduction Mitosis  It is very important that all of the DNA gets copied correctly and equally divided among the new nuclei so that the 2 new cells are exactly the same.  Incorrectly divided/copied DNA results in a mutation and possible cell death Section 2

Cellular Reproduction The Stages of Mitosis  There are 4 phases of Mitosis  Prophase – Pro’s are first  Metaphase – Middle; chromosomes align in the middle  Anaphase – Apart; chromosomes pulled apart  Telophase – Two nuclei Section 2

Cellular Reproduction The Stages of Mitosis - First  Prophase  The cell’s chromatin (DNA) scrunches together, it tightens and condenses as X shaped chromosomes.  Sister chromatids are attached at the centromere, the center of the chromosome Section 2

Cellular Reproduction  The nuclear envelope and nucleolus seem to disappear.  Spindle fibers form in the cytoplasm. Section 2  Prophase

Cellular Reproduction Metaphase Spindle fibers attach to the chromosomes. Chromosomes align toward the center of the cell. They line up along the middle of the cell. Section 2

Cellular Reproduction Anaphase Section 2  The microtubules of the spindle apparatus begin to shorten.  The sister chromatids separate and pull apart.  The chromosomes move toward the poles of the cell.

Cellular Reproduction Telophase Section 2  Two new nuclear membranes begin to form around the DNA and the nucleoli reappear.  The spindle apparatus disassembles  Chromosomes decondense or relax

PROPHAS E METAPHA SE ANAPHAS E TELOPHAS E

Cellular Reproduction The Stages of Mitosis  Prophase – Pro’s are first  Metaphase – Middle; chromosomes align in the middle  Anaphase – Apart; chromosomes pulled apart  Telophase – Two nuclei Section 2

Cellular Reproduction Cytokinesis  Cytokinesis is the final step of the cell cycle where the cell’s cytoplasm divides into 2 new cells  In animal cells: a cleavage furrow forms where microfilaments constrict, or pinch, the cytoplasm.  In plant cells: a cell plate forms which is a new structure that divides the cell. Section 2

Cellular Reproduction Cytokinesis Section 2

Cellular Reproduction Mitosis Section 2 Mitosis and Cytokinesis

Cell Cycle Regulation Cellular Reproduction Normal Cell Cycle  The cell cycle has built-in checkpoints that monitor the cycle and can stop it if something goes wrong.  If the cell cycle is not monitored, then cancer can result. Section 3

Cellular Reproduction Abnormal Cell Cycle: Cancer  Cancer is the uncontrolled growth and division of cells.  Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function. Section 3 Cell Cycle Regulation

Cellular Reproduction Causes of Cancer  The changes that occur in the regulation of cell growth and division of cancer cells are due to mutations.  Various environmental factors can affect the occurrence of cancer cells.  Cigarette smoke – lung cancer  Asbestos – lung cancer  Sun Exposure – skin cancer and cataracts Section 3 Cell Cycle Regulation

Cellular Reproduction Section 3 Cell Cycle Regulation