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Cell Division Chapter 10. Anatomy of a Chromosome. Chromosome- coils of DNA and proteins. Centromere- where the two chromatids attach. Chromatid - two exact copies of DNA that make up a chromosome. Limits to Cell Growth DNA Overload
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Chromosome- coils of DNA and proteins Centromere- where the two chromatids attach Chromatid- two exact copies of DNA that make up a chromosome
Limits to Cell Growth • DNA Overload • The larger a cell becomes, the more demands the cell places on its DNA • Exchanging Material • The cell has trouble moving enough nutrients and wastes across the cell membrane if the cell is too big. • Surface Area:Volume ratio can’t be too small
Cell Cycle • Interphase (inter- means “between”) • G1 phase – Cell growth • S phase – DNA replication • G2 phase – preparation for cell division • Cells are in interphase most of the time. • M phase • Mitosis: prophase, metaphase, anaphase, telophase, cytokinesis • G0 phase • Cells that cannot divide like nerve cells, red blood cells, and cardiac cells
Pair of centrioles Prophase A? B? C? D? • What are the important events happening during Prophase? Plant cells in prophase
Pair of centrioles Prophase Plant cells in prophase • Chromosomes condense into sister chromatids • Chromatids are joined by a centromere • Centrioles appear and form mitotic spindle • Nucleolus disappears and nuclear envelope dissolves • Longest phase of mitosis (50-60%)
Metaphase A? B? C? D? • What events are occurring during Metaphase? Animal cell Plant cell
Metaphase • Centrioles on opposite ends of the cell • Microtubules of mitotic spindle attach to the centromeres • Chromosomes line up across the middle (equator) of the cell Animal cell Plant cell
Anaphase A? B? C? D? • What important events are occurring at Anaphase? Early anaphase (plant) Late anaphase (plant) Anaphase (animal)
Anaphase • Sister chromatids separate • Chromosomes migrate to opposite ends of the cell Early anaphase (plant) Late anaphase (plant) Anaphase (animal)
Telophase Plant cell Animal cell A? B? C? D? • What important events happen during Telophase?
Telophase Plant cell Animal cell • Chromosomes begin to disperse • Nuclear envelopes reform • Mitotic spindle breaks apart
Cytokinesis Difficult to distinguish from telophase In animal cells the cell membrane pinches in forming two daughter cells In plant cells a cell plate forms between the daughter nuclei and a new cell wall forms at the cell plate Animal cell Plant cell
Which stage is each photo in?? How do you know??
Interphase Now its YOUR turn! What are the important events at each phase? G1 phase –?? S phase –?? G2 phase –?? What types of cells would be in G0 phase??
Cancer • Uncontrolled cell growth • Caused by smoking, exposure to radiation or certain chemicals, some viruses • Cancer cells smother normal cells • Treatment options • Surgery to remove tumor • Radiation therapy to halt cell division • Chemotherapy to halt cell division