Cell Division
Laura Armstrong & Joe Wolfensohn
Teachers
Contents
Recall Questions
This topic requires prior knowledge of the cell cycle (from GCSE) and the structural organisation of chromosomes. You can test your knowledge on these below.
What are the two main types of cell division?
Mitosis and meiosis.
Why is cell division necessary?
- Growth and repair of tissues
- Reproduction
Describe the structure of DNA in the nucleus of a eukaryotic cell.
- A double helix of 2 polymer strands made of many nucleotides
- DNA nucleotides contain deoxyribose sugar, a phosphate group and a nitrogenous base
- DNA is wrapped around histone proteins
Topic Explainer Video
Check out this @JoeDoesBiology video that explains cell division or read the full notes below. Once you've gone through the whole note, try out the practice questions!
Cell Division and The Cell Cycle
Cell Division
- The process by which a parent cell divides to produce new cells.
- Essential for growth, repair of tissues and reproduction.
- There are 3 types of cell division; mitosis, meiosis and binary fission (in bacteria).
Reasons for Cell Division
- Growth: Multicellular organisms grow by increasing the number of cells.
- Repair and Maintenance: Damaged or old cells are replaced via mitosis.
Reproduction:
- Asexual reproduction (mitosis) in unicellular organisms.
- Sexual reproduction (meiosis) in gamete formation.
The Cell Cycle
- Interphase: The cell grows and prepares for division.
- Mitosis: The nucleus divides (covered in a separate study note).
- Cytokinesis: The cytoplasm and cell membrane divides.
How The Cell Prepares for Division
- Growth and Organelle Production: Ensures the cell has enough cytoplasm and organelles for division.
- DNA Replication: Copies the entire genetic material.
- Checking for Errors: The cell checks for DNA mutations before proceeding.
Interphase: The Longest Phase
- G1 Phase (Gap 1): Cell grows and produces new organelles, for example, ribosomes and mitochondria are replicated.
- S Phase (Synthesis): DNA replication occurs.
- G2 Phase (Gap 2): Further growth and preparation for mitosis.
- G0 Phase: Immediately after cytokinesis. A resting phase where cells do not divide.
Key Characteristics of Interphase
- Chromosomes are not visible under a light microscope as they are not condensed.
- There is a DNA checkpoint before entering mitosis. The cell checks for DNA mutations before proceeding into mitosis.
Key Terms
- Mitosis: Division of the nucleus.
- Cytokinesis: Division of the cytoplasm.
- Interphase: Stage of the cell cycle where the cell grows, organelles increase in number and DNA is replicated.
No answer provided.
Exam Tips
Use precise terminology (e.g., "DNA replication" instead of "DNA copied").
No answer provided.
Explain the importance of interphase in the cell cycle. (4 marks)
- Interphase allows for cell growth.
- DNA replication occurs during the S phase to ensure daughter cells have the full set of DNA.
- The cell undergoes checks for DNA errors before mitosis.
- Organelles are replicated before division, such as mitochondria.
Practice Question
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!