Overview
This lesson covers the M phase of the cell cycle, focusing on the steps and processes of mitosis and cytokinesis during cell division.
Cell Cycle Overview
- Interphase consists of G1, S, and G2 phases.
- The M phase is the final phase and represents cell division.
- Cell division includes mitosis (nuclear division) and cytokinesis (cytoplasmic division).
Mitosis: Four Phases
- Mitosis is divided into four phases: prophase, metaphase, anaphase, and telophase.
Prophase
- Chromatin condenses into visible chromosomes and nucleolus disappears.
- Each chromosome consists of two sister chromatids joined at a centromere.
- Spindle fibers form from centrioles, which move to opposite cell poles.
- Nuclear membrane disintegrates, allowing spindle fibers to attach to centromeres.
Metaphase
- Centrioles reach cell poles and spindle fibers align chromosomes along the cell equator.
- Sister chromatids are positioned on opposite sides of the equator.
Anaphase
- Spindle fibers pull sister chromatids apart at centromeres, now called chromosomes.
- Chromosomes move in a V-shape towards opposite poles.
Telophase
- New nuclear membranes form around each chromosome set.
- Chromosomes decondense into chromatin and nucleolus reappears.
- Nuclear division (mitosis) is complete.
Cytokinesis
- Cytokinesis divides the cytoplasm after mitosis is done.
- In animal cells, the membrane pinches inward to split the cell into two.
- In plant cells, a cell plate forms at the equator to separate the two new cells, which will later develop new cell walls.
M Phase Summary & Results
- M phase consists of mitosis and cytokinesis, producing two genetically identical daughter cells.
- Both daughter cells are identical to each other and to the original parent cell.
Key Terms & Definitions
- Interphase — stage before cell division including G1, S, and G2 phases.
- M phase — phase where cell division occurs, including mitosis and cytokinesis.
- Mitosis — division of the cell nucleus into two identical nuclei.
- Cytokinesis — division of the cytoplasm, forming two separate cells.
- Chromatin — loosely organized DNA and protein complex in the nucleus.
- Chromosome — condensed form of DNA visible during mitosis.
- Sister Chromatid — one of two identical DNA strands in a duplicated chromosome.
- Centromere — region attaching sister chromatids together.
- Centriole — structure at cell poles organizing spindle fibers.
- Spindle fiber — microtubules that separate chromosomes during mitosis.
- Cell plate — structure that forms in plant cells during cytokinesis to separate daughter cells.
Action Items / Next Steps
- Review diagrams of mitosis phases.
- Study differences between animal and plant cell cytokinesis.
- Prepare for quizzes on cell cycle stages and mitosis terminology.