Chapter 3: From a Cell to an Organism Lesson 1: The Cell Cycle and Cell Division PDF

**Chapter 3: From a Cell to an Organism** **Lesson 1: The Cell Cycle and Cell Division** **Cell Cycle:** most cells in an organism go through a cycle of growth, development, and division - Through the cell cycle, organisms grow, develop, replace old and damaged cells, and produce new cells....

**Chapter 3: From a Cell to an Organism** **Lesson 1: The Cell Cycle and Cell Division** **Cell Cycle:** most cells in an organism go through a cycle of growth, development, and division - Through the cell cycle, organisms grow, develop, replace old and damaged cells, and produce new cells. Two main stages in the cell cycle: 1. **Interphase:** the period during the cell cycle of a cell's growth and development a. **A cell spends most of its life in interphase.** b. **Most cells go through 3 stages:** i. **Rapid growth and replication, or copying, of the membrane-bound structures (called organelles)** ii. **Copying of DNA, the genetic information of the cell** iii. **Preparation for cell division** 2. **Mitotic phase:** in eukaryotic cells, a process of cell division that form two new nuclei, each of which has the same number of chromosomes c. **Shorter phase then interphase** d. **The cell reproduces during this phase.** e. **Has 2 stages: mitosis and cytokinesis** iv. **In mitosis, the nucleus divides** v. **In cytokinesis, the cytoplasm divides** vi. **This phase creates 2 new identical cells. The original cell no longer exists.** f. **The time it takes a cell to complete the cell cycle depends on the type of cell that is dividing.** vii. **Most human cells complete the cell cycle in 24 hours.** Interphase makes up most of the cell cycle and the longest time. It has a few key points. - Begins with a period of rapid growth -- the cell gets bigger. - Followed by cellular activities such as making proteins. - Makes copies of its DNA and prepares for cell division. - DNA is called chromatin during interphase. - Chromatin: long, thin strands of DNA Molecular Expressions Cell Biology: Chromatin and Chromosomes +-----------------------+-----------------------+-----------------------+ | **Phase** | **Stage** | **Description** | +=======================+=======================+=======================+ | **Interphase** | G~1~ phase | Rapid cell growth, | | | | protein production -- | | | | longest stage of the | | | | cell cycle -- carries | | | | out normal cell | | | | functions | +-----------------------+-----------------------+-----------------------+ | | S phase | DNA duplication | | | | | | | | (makes a copy) | +-----------------------+-----------------------+-----------------------+ | | G~2~ phase | Preparation for | | | | division | +-----------------------+-----------------------+-----------------------+ | **Mitotic phase** | **Mitosis** | *[Prophase]{.underlin | | | | e}* | | | | -- copied DNA | | | | condenses into | | | | chromosomes | +-----------------------+-----------------------+-----------------------+ | | | *[Metaphase]{.underli | | | | ne}* | | | | -- chromosomes line | | | | up in the middle | +-----------------------+-----------------------+-----------------------+ | | | *[Anaphase]{.underlin | | | | e}* | | | | -- sister chromatids | | | | separate and are | | | | pulled to opposite | | | | ends | +-----------------------+-----------------------+-----------------------+ | | | *[Telophase]{.underli | | | | ne}* | | | | -- nuclear membrane | | | | forms around the | | | | chromatin and two | | | | nuclei start to form | +-----------------------+-----------------------+-----------------------+ | | **Cytokinesis** | The cytoplasm and its | | | | contents divide | | | | resulting in two | | | | identical nuclei | +-----------------------+-----------------------+-----------------------+ S phase DNA: - **Sister chromatids:** two identical chromosomes -- makes up a duplicated chromosome - **Centromere:** sister chromatids are held together by this structure - **The joined chromatids twist and coil and condense into an X shape.**  The **Mitotic Phase -- 2 stages** 1. **Mitosis:** the nucleus and its contents divide a. **Divided into 4 phases:** i. *Prophase:* the nuclear membrane dissolves and chromosomes condense into rodlike structures 1. The nucleolus disappears and the nuclear membrane disappears. 2. Spindle fibers form in the cytoplasm. ii. *Metaphase:* chromosomes lie up along the equator of the cell (middle of the cell) 3. The spindle fibers push and pull the duplicated chromosomes to the middle of the cell. 4. Shortest phase in mitosis. iii. *Anaphase:* chromatids separate and move to opposite sides of the cell 5. The spindle fibers pull them in opposite directions. 6. This phase is complete when each identical sets of chromosomes are at opposite ends of the cell. iv. *Telophase:* nuclear membrane forms around each set of chromosomes...mitosis is complete 7. The spindle fibers begin to disappear. 8. The chromosomes begin to uncoil. 9. Called the reverse of prophase. 3. **Cytokinesis:** the division of the cytoplasm of a cell g. **Daughter cells:** the two new cells that result from mitosis and cytokinesis. h. The cell begins to pinch inward and eventually pinches all the way through creating a crease called a furrow in the middle of the cell. viii. The cell splits into 2 cells -- these cells are identical to each other i. In plants, a cell plate forms in the middle of the cell. j. The original cell no longer exist but two new cells are formed. ix. These cells are identical to each other. Results of cell division: 1. Reproduction a. This occurs in some unicellular organisms like bacteria. 2. Growth b. This allows multicellular organisms to grown and develop from one cell to many cells. 3. Replacement c. This allows cells that wear out or are damaged to be replaced with healthy cells. 4. Repair d. Cells that have been damaged can go through cell division to repair areas like broken bone or cuts. e. Not all cells can repair. Damages to nerve cells are permanent because nerve cells stop the cell cycle when those cells are mature. Interphase + Mitosis