Limits to Cell Growth There are two main reasons why cells divide rather than continuing to grow indefinitely.         The larger a cell becomes, the more demands the cell places on its DNA. In addition, the cell has more trouble moving enough nutrients and wastes across the cell membrane. 1 1 1

Think of the Kitchen in your House as the cell’s nucleus. Would your kitchen be able to do it’s job if your family size doubled? Why or why not? Would your kitchen work for this school? Could it produce enough food? How would you get all the supplies (food) into your kitchen? Where would all the waste go? Do you have enough trash cans?

1 A large cell that has trouble exchanging materials is like a small town with a  A.fire department that does not have enough trucks. B.main street that is too narrow. C.library that does not have enough books.

2 The process by which a cell divides into two new daughter cells is called  A.cell growth. B.cell division. C.DNA replication.

Asexual reproduction leads to two cells with the exact same DNA Asexual reproduction leads to two cells with the exact same DNA. All of your cells came from on cell originally. If all your cells have the same DNA, then why are your cells different? Your skin cells are different than your heart cells and different than your blood cells.

Three reasons why cells reproduce by asexual reproduction: 1. Growth 2 Three reasons why cells reproduce by asexual reproduction: 1. Growth 2. Repair 3. Replacement Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun. Cell that reproduce by asexual reproduction reproduce constantly.

Mitosis Interphase (G1, S, G2) Prophase Metaphase Anaphase Cell division occurs in a series of stages, or phases. Interphase (G1, S, G2) Prophase Metaphase Anaphase Telophase & Cytokinesis

3 Which of the following phases is the first step in mitosis? Prophase Telophase Metaphase Anaphase

Interphase occurs before mitosis begins Chromosomes are copied (# doubles) Chromosomes appear as threadlike coils (chromatin) at the start, but each chromosome and its copy(sister chromosome) change to sister chromatids at end of this phase CELL MEMBRANE Nucleus Cytoplasm

Interphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Prophase 1st step in Mitosis Mitosis begins (cell begins to divide) Centrioles (or poles) appear and begin to move to opposite end of the cell. Spindle fibers form between the poles. Centrioles Sister chromatids Spindle fibers

Prophase Plant Cell Animal Cell Spindle fibers Centrioles Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Metaphase 2nd step in Mitosis Chromatids (or pairs of chromosomes) attach to the spindle fibers. Centrioles Spindle fibers

Metaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Anaphase 3rd step in Mitosis Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell. Centrioles Spindle fibers

Anaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Telophase 4th step in Mitosis Two new nuclei form. Chromosomes appear as chromatin (threads rather than rods). Mitosis ends. Nuclei Nuclei Chromatin

Telophase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Cytokinesis occurs after mitosis Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes.

4 The process of DNA replication is necessary before a cell — codes for RNA molecules modifies lysosome enzymes divides into two cells makes a protein

Animal Mitosis -- Review Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

Plant Mitosis -- Review Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

5 What is the correct sequence for plant cell mitosis? A, B, D, C C, B, A, D B, A, D, C D, C, B, A

6 Which phase of mitosis would be seen next? A B C D

Cell Cycle

- Cell Division The Cell Cycle 28

The Cell Cycle 29 29

Mitosis Animation http://www.cellsalive.com/mitosis.htm