Overview
This lecture explains the importance of mitosis, the stages of the cell cycle involving mitosis, and why cells need to divide.
Chromosomes and Genes
- Both plant and animal cells have a nucleus containing chromosomes made of DNA.
- Body cells contain chromosomes in pairs (human cells have 23 pairs).
- Gametes (sex cells) do not have paired chromosomes (covered in a later lesson).
- Chromosomes carry genes, which determine many features of an organism.
The Cell Cycle and Mitosis
- The cell cycle is how cells divide and includes mitosis and another process called meiosis (meiosis covered separately).
- The cell cycle including mitosis has three main stages.
Stages of the Cell Cycle Involving Mitosis
- Stage 1: DNA replicates to form two copies of each chromosome; the cell grows and copies internal structures (e.g., mitochondria, ribosomes).
- Stage 2 (Mitosis): One set of chromosomes is pulled to each cell end; the nucleus divides.
- Stage 3: The cytoplasm and cell membrane divide, creating two identical cells with the same number of chromosomes as the original.
Functions and Importance of Mitosis
- Mitosis is essential for growth and development in multicellular organisms (e.g., plants and animals).
- Mitosis enables repair of organisms, such as healing broken bones.
- Mitosis occurs during asexual reproduction.
Key Terms & Definitions
- Chromosome — a DNA molecule containing genetic information in the form of genes.
- Gene — a segment of DNA that determines specific characteristics.
- Mitosis — a process where a cell divides to produce two identical cells.
- Cell Cycle — the sequence of growth and division of a cell.
- Cytoplasm — the material within a cell, excluding the nucleus.
- Multicellular Organism — an organism made up of more than one cell.
Action Items / Next Steps
- Review the stages of the cell cycle and their order.
- Prepare for questions about mitosis and the cell cycle for exams.
- Optional: Consult the recommended revision workbook for practice questions.