Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
National 4 and 5- Cell Division Investigating Cell Division Cell division is the way in which an organism increases its number of cells. division means different things for unicellular and multicellular organisms: Cell Unicellular - Cell division results in the production of a new organism. Multicellular - Cell division results in growth of the organism and repair damaged parts. Division of plant and animal cells Cell division, and all other activities, of both plant and animal cells are controlled by the nucleus. The nucleus contains thin, threadlike structures called chromosomes that carry all the cells information: Chromatid Centromere Chromatid After cell division, the two cells produced contain exactly the same number of chromosomes and therefore all of the cells information. The process by which this occurs is called mitosis. 1 Mitosis 1. Chromosomes coil up and become shorter and thicker. Then can now be stained and viewed under a microscope. 2. Chromosomes line up along the equator (centre) of the cell and a spindle forms, attaching to the centromere of each chromosome. 3. The centromere splits and each chromatid is pulled to the opposite poles (ends) of the cell. 4. A nuclear membrane forms around each clump of chromatids and the cytoplasm begins to divide. 5. The cytoplasm divides completely and the separated chromatids are now known as chromosomes. 6. Each cell grows, and while this is happening the chromosomes uncoil and replicate to produce two identical chromatids. Once the chromosomes have uncoiled it is no longer possible to view them under a microscope. 2 Chromosome Complement Chromosomes contain the information that determines the characteristics of every cell in an organism. Consequently, chromosomes determine what characteristics an organism possesses and what characteristics it does not. Every species of plant and animal has a characteristic number of chromosomes in each of its cells. This number is known as the chromosome complement. In order for an organism to have all the characteristics of it’s species it must have all of the chromosomes of that species (a complete complement of chromosomes) in its cells. Mitosis ensures that all of the chromosomes of a cell are passed on when that cell divides. Diploid cells have two matching sets of chromosome which are replicated during mitosis. Cancer Cancer is an example of uncontrolled cell division. Cell culture (Covered in more detail in therapeutic uses of cells later) Cell production by cell culture requires aseptic technique and appropriate medium. Factors such and oxygen concentration, temperature and pH can affect the growth of cells. In any work using microorganisms a great deal of care has to be taken. This is to ensure that any unwanted microorganisms are not grown and released to surroundings. In the lab: 1. 2. 3. 4. 5. 6. 7. 8. 9. Always wear a lab coat and safety glasses. Wash your hands before starting. Wipe work surfaces with disinfectant. Use only sterilised equipment. Dispose of materials safely. Wipe surfaces again. Wash hands when finished. Do not eat or drink. Never open dishes containing microbes. 3 These precautions must also be taken in biotechnological processes to avoid contamination. Check point A2 Level 4 E&O By researching cell division, I can explain its role in growth and repair and can discuss how some cell can be used therapeutically 4.13 a Nat 4 cell division and its role in growth and repair Cell division is essential to allow organism to grow and repair damaged parts. During cell division, the parent cell divides to produce two identical cells, which contain the same number of chromosomes in the nuclei as the parent cell. Cancer is uncontrolled cell division. Nat 5 Producing new cells a. Maintenance of diploid chromosome complement by mitosis. b. Sequence of events of mitosis, including the terms chromatids, equator and spindle fibres. c. Cell production by cell culture requires aseptic techniques, an appropriate medium and the control of other factors. d. Mitosis is required for growth and repair 4