AQA Biology Year 12 A level - 3.2.2 Cell Division

Sep 5, 2026

Year 12 A level AQA Biology notes for section 3.2.2 Cell Division, covering the cell cycle, interphase, mitosis and meiosis, and the biological need for cell division in multicellular organisms. The material explains how specialised cells transition through G1, may enter the resting G0 phase, and how DNA replication in interphase ensures equal genetic content for daughter cells. It also links mitosis to growth, repair and tissue replacement, and introduces cancerous tumour formation. Includes definitions of key terms used across the lesson.

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3.2.2 Cell Division

Lesson 1 - The Cell Cycle

Specification Key Word List

AQA Biology Year 12 A level 3.2.2 Cell Division Name: | Lesson | Exam Question Marks | Homework Checked | Date | | --- | --- | --- | --- | | 1 – The Cell Cycle | /28 | | | | 2 – Stages of Mitosis | /31 | | | | 4 – Observing Mitosis Practical Techniques | /35 | | | | 3 – Cancer | /34 | | | | 4 – Binary Fission | /5 | | | Specification Sections Key word list | Anaphase | The third stage of Mitosis; the centromere splits and one chromatid is pulled into opposite ends of the cell. | | --- | --- | | Cancer | A disease, resulting from mutations, that leads to uncontrolled cell division and the eventual formation of a group of abnormal cells called a tumour | | Carcinogen | A chemical, form of radiation or other agent that causes cancer | | Cell Cycle | The series of events that take place in a cell leading to its division and duplication. | | Centriole | structures that form during the cell cycle responsible for the formation of spindle fibres. | | Centromere | The centre structure within a chromosome that joins the chromatids | | Chromatid | One of the two copies of a chromosome that are joined together by a single centromere prior to cell division | | Chromatin | Uncondensed DNA when it is not wound up tightly as a chromosome | | Chromosome | A thread-like structure made of protein and DNA by which hereditary information is physically passed from one generation to the next | | Clone | A group of genetically identical organisms formed from a single parent as a result of asexual reproduction or by artificial means | | Cytokinesis | The process in which the cytoplasm of a single eukaryotic cell is divided to form two daughter cells following the telophase of Mitosis and Meiosis. | | Differentiation | The process by which cells become specialised for different functions | | Diploid | Cells in which the nucleus contains two sets of chromosomes | | DNA replication | The process by which a cell makes a copy of the DNA found within the nucleus. | | Homologous
chromosomes | A pair of chromosomes, one maternal and one paternal, that have the same gene loci and therefore determine the same features. | | Interphase | The longest phase of the cell cycle in which the cell increases in size and makes a copy of its DNA. | | Metaphase | The second stage of mitosis; chromosomes line-up along centre of the cell & spindle fibres attach to the centromere of each chromosome | | Mitosis | The type of nuclear division in which the daughter cells have the same number of chromosomes as the parent cell | | Mutagen | Any agent that induces a mutation | | Mutation | A sudden change in the amount or the arrangement of the genetic material in the cell | | Photomicrograph | Photograph of an image produced by a microscope | | Prokaryotic cell | A cell that does not have a nucleus or membrane bound organelles | | Prophase | The first stage of Mitosis; chromatin in the nucleus condenses to form chromosomes | | Spindle Fibre | Fibre-like structure that pulls or separates the chromosomes into the daughter cells during cell division. | | Stem cell | Undifferentiated dividing cells that occur in embryos and in adult animal tissues that require constant replacement | | Telophase | The fourth stage of mitosis; a new nucleus forms around the chromatids as they lose their shape and return to chromatin. | | Tissue | A group of similar cells organised into a structural unit that serves a particular function | | Tumour | A swelling in an organism that is made up of cells that continue to divide in an abnormal way | | Tumour
suppressor gene | A gene that maintains normal rates of cell division and so prevents the development of tumours | Lesson 1 – The Cell Cycle By the end of this lesson you should be able to: • Explain the uses of cell division by meiosis and mitosis • Describe the stages of the cell cycle Notes: Cell division must occur in multicellular organisms in order for them to grow and to replace damaged or worn out tissue.

FAQs

What are mitosis and meiosis used for in the cell cycle?

Mitosis supports growth, replacement of lost cells, repairing damaged tissue, and can form clones in immune responses. Meiosis occurs in reproductive organs to produce haploid sex cells for sexual reproduction.

What happens during interphase (G1, S, and G2)?

During G1 the cell elongates and makes new organelles and proteins. In S phase it replicates DNA so the amount of DNA doubles, and in G2 it continues preparing by making proteins needed for cell division.

Why do multicellular organisms need cell division?

Cell division is required for organisms to grow and to replace damaged or worn-out tissue. Many specialised cells do not repeatedly divide and instead rely on stem cells for replacement.

Sep 5, 2026

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