Cell Cycle & Mitosis PDF

Cell Cycle in Plants The cell cycle is the series of events that cells go through to grow and divide into two identical daughter cells. Eukaryotic Cells 1- Somatic cells: Cells that make your organs and tissues. 2- Sex Cells: sperm and egg (Gametes). Importance of the Cell Cycle in Plants Growth...

Cell Cycle in Plants The cell cycle is the series of events that cells go through to grow and divide into two identical daughter cells. Eukaryotic Cells 1- Somatic cells: Cells that make your organs and tissues. 2- Sex Cells: sperm and egg (Gametes). Importance of the Cell Cycle in Plants Growth : The cycle drives the growth of roots, stems, and leaves. Development : It allows the formation of specialized tissues during plant maturation. Repair : Damaged cells are replaced through the production of new cells. Reproduction: Through meiosis produces gametes for sexual reproduction. The cycle consists of two main parts: 1. Interphase: (growth and DNA replication). 2. M phase (Mitotic phase): (cell division).  Phases of the Cell Cycle 1. Interphase (G1, S, G2) This phase is the cell’s preparation stage for division and is divided into three sub- phases: i. G1 phase (Post-Mitotic Gap phase) ( 10:12 h) "Get Big" - The cell increases in size to prepare for the upcoming DNA replication. - The cell synthesize organelles and proteins that are needed for DNA replication. - The cell conducts a checkpoint to ensure it's ready for DNA replication. Nucleus in G1 Have DNA equivalent to (2n) ii. S phase ( 7:8 h) " Synthesize " - DNA replication occurs, meaning the cell duplicates its entire genome. - DNA remains in its loose, uncondensed chromatin state. - Synthesis of Histone protein takes place. Nucleus in S phase Have DNA equivalent to (4n) iii. G2 phase (Pre-Mitotic Gap phase) ( 2:5 h) "Get Ready" - The cell continues to grow and produce more proteins and organelles needed for mitosis. - Synthesis of proteins that required for spindle fibers formation takes place. - The cell checks for any errors in the duplicated DNA and repairs them. Nucleus in G2 Have DNA equivalent to (4n)  2. M phase (Mitotic phase) The M phase is the part of the cell cycle where the cell actually divides. It consists of: i. Mitosis (nuclear division) ii. Cytokinesis (cytoplasmic division). A. Mitosis (PMAT: Prophase, Metaphase, Anaphase, Telophase) 1) Prophase " Prepare" - The chromatin condenses into visible chromosomes, each consisting of two sister chromatids. - The nuclear envelope breaks down, releasing the chromosomes into the cytoplasm. - Spindle fibers begin to form and extend from the spindle poles toward the chromosomes. - In plant cells, there are no centrioles, but the spindle fibers organize from specific regions. (Prepare = Chromosomes condense, nuclear envelope dissolves, and spindle forms.) 2) Metaphase " Middle" - The chromosomes align in the center of the cell at the metaphase plate (the cell’s equator). - Each chromosome’s centromere is attached to the spindle fibers from opposite poles. - (Middle = the chromosomes align in the middle of the cell.) 3) Anaphase " Away" - The spindle fibers shorten, pulling the sister chromatids apart to opposite poles of the cell. - Each chromatid now becomes an individual chromosome. - The cell elongates as the spindle fibers push the poles of the cell further apart. - (Apart, as the sister chromatids are pulled apart.) 4) Telophase " Two" - Two new nuclear envelopes form around the separated chromosomes at each pole. - The chromosomes de-condense back into the loose chromatin state. - The spindle fibers break down and disappear. - At this point, there are now two distinct nuclei within the cell. - (Two= two new nuclei form.) B. Cytokinesis " Cutting " - What happens: - The cytoplasm divides, creating two distinct daughter cells. - In Animal cells, a cleavage furrow forms in the center of the cell. - In plant cells, a cell plate forms in the center of the cell, growing outward eventually fusing with the cell wall, which becomes the new cell wall separating the two cells. - Each daughter cell is genetically identical to the original cell, containing a full set of chromosomes. (Cut, as the cytoplasm is cut in half to create two cells.)