Overview
This lecture covers the cell cycle with a focus on mitosis, detailing the phases and importance of cell division for growth, repair, and reproduction.
The Cell Cycle
- The cell cycle is the full life cycle of a cell, including growth and division.
- Interphase is where a cell spends about 90% of its life, performing normal functions and preparing to divide.
- Interphase consists of G1 (cell growth), S (DNA synthesis/replication), and G2 (further growth).
DNA Replication and Preparation
- DNA replication happens during the S phase to ensure new cells have identical DNA.
- Cells must fully replicate DNA before beginning cell division.
Mitosis: Phases and Events
- Mitosis is somatic (body cell) division, following interphase.
- Mitosis includes four main phases: prophase, metaphase, anaphase, and telophase, followed by cytokinesis.
Prophase
- DNA condenses into chromosomes to make separation easier.
- The nuclear envelope breaks down so chromosomes can be accessed.
- The mitotic spindle, a protein structure, forms to help separate chromosomes.
Metaphase
- Chromosomes line up along the middle (equator) of the cell.
- The mitotic spindle attaches to chromosomes in preparation for division.
Anaphase
- Chromosomes are pulled apart to opposite sides of the cell by the mitotic spindle.
Telophase and Cytokinesis
- Chromosomes uncoil back to their loose form.
- The nuclear envelope reforms around each set of DNA.
- The cell splits into two identical cells, each with the same amount of DNA as the original.
Practice Question Review
- Chromosome structures (condensed chromosomes) form during prophase.
Key Terms & Definitions
- Cell Cycle — the complete life cycle of a cell, including growth and division.
- Interphase — phase where the cell grows and prepares for division.
- G1 and G2 Phases — periods of cell growth before and after DNA replication.
- S Phase — the phase where DNA is replicated.
- Mitosis — process of somatic cell division consisting of prophase, metaphase, anaphase, telophase, and cytokinesis.
- Chromosome — condensed structure of DNA formed during cell division.
- Mitotic Spindle — protein structure that separates chromosomes.
- Cytokinesis — splitting of the cell into two after mitosis.
Action Items / Next Steps
- Review and memorize the phases of mitosis and their key events.
- Be able to identify at which phase chromosome structures form (prophase).