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Cell division
| Term | Definition |
|---|---|
| Cell continuity | Cells arise from pre-existing cells. |
| Chromosomes | Thread like structures made up of DNA and protein |
| Homologous pairs | Pairs of chromosomes that contain genes that control the same characteristics |
| Genes | Short sections of DNA that code for a protein Control features such as eye colour and hair colour |
| Locus | The position of a gene on a chromosome |
| Haploid cells | A cell whose nucleus only contains one set or copy of chromosomes |
| How haploid is represented | The letter ‘n’ |
| Haploid cell in the human body | Gametes |
| Gametes | Sex cells i.e egg and sperm cells |
| Diploid cells | A cell whose nucleus contains two sets or copies of each chromosome |
| How diploid cells are represented | ‘2n’ |
| Example of a diploid cell | Somatic (normal body cells) |
| The cell cycle definition | A series of changes that occur in a cell, during the period between one cell division and the next |
| Interphase | The period of time when the cell is not dividing |
| Phase that takes up most of the cycle | Interphase |
| What happens during interphase | The cell prepares for division by growing in size/growth It replicates its DNA Protein synthesis Animal cells - respiration Plant cells - photosynthesis |
| Chromatin definition and function | Elongated DNA Condense to form visible strands under the microscope which we call chromosomes |
| Mitosis | Cell division that forms two identical daughter cells (Nuclear division that forms two identical nuclei) Maintains the chromosome number |
| Function of mitosis in unicellular organisms e.g amoeba | Main function is to reproduce (asexually) |
| Function of mitosis in multicellular organisms | Growth Repair of tissue |
| Type of cells mitosis occurs in | Eukaryotic organisms |
| The equivalent process in prokaryotic organisms | Binary fission |
| Stages involved in mitosis (4) | 1. Prophase 2. Metaphase 3. Anaphase 4. Telaphase |
| Prophase steps | Chromatin condenses to form double stranded chromosomes which are joined by a structure called a centromere. The nuclear membrane gradually breaks down, disappears Spindle fibres form around the centrioles. |
| Metaphase steps | Centrioles send out spindle fibres Chromosomes line up along the equator of the cell. |
| Anaphase steps | Spindle fibres contract. Centromere splits and separates the sister chromatids. One chromosome is pulled to the opposite ends of the cell. |
| Telophase steps | Chromosomes lengthen Spindle fibres break down, disappear Nuclear membranes reform at each pole |
| Cytokinesis in an animal cell | The cell membrane pinches in forming a cleavage furrow. Two cells separate |
| Cytokinesis in a plant cell | Vesicles gather along the middle of the cell forming a cell plate. This eventually forms a cell wall and the cells separate |
| Cancer | A group of disorders due to the uncontrolled rate of mitosis (cell division) |
| Tumors | Abnormal cells form masses called tumours Benign tumours usually don’t cause serious problems and can be removed with surgery. Malignant tumours are invasive and disrupt the normal functions of tissues or organs. |
| Causes of cancer (carcinogens) | Uv rays Chemicals e.g cigarette smoke, asbestos Viruses eg HPV Alchahol |
| Cancer treatments | Surgery Chemotherapy Radiotherapy |
| Chemotherapy | Chemicals introduced to bloodstream to attack and kill dividing cells. |
| Radiotherapy | Radiation passed through the tumour to kill the cells |
| Example of cells that don’t undergo mitosis | Red blood cells |
| Why blood cells don’t undergo mitosis | They don’t have a nucleus |
| Meiosis | Cell division where four daughter cells are produced with half the number of chromosomes of the parent cell |
| Where meiosis occurs | In the reproductive system to produce gametes |
| Functions of meiosis | 1. Produce gametes 2. Halves the chromosome number 3. Variation - daughter cells are not identical |
Created by:
EObrienHart
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