LIFE SCIENCES GRADE 10 CAPS STRUCTURED CLEAR PRACTICAL

LIFE SCIENCES GRADE 10 CAPS STRUCTURED, CLEAR, PRACTICAL - HELPING TEACHERS UNLOCK THE POWER OF NCS KNOWLEDGE AREA: Life at Molecular, Cellular and Tissue Level TOPIC 1. 3: Cell Division The Cell Cycle. Mitosis

SUMMARY OF PRESENTATION Introduction Cell cycle Process of mitosis Mitosis in plant and animal cell Importance of mitosis Cancer

INTRODUCTION � Before we start with cell division there are some terms that we need to understand. � The body is made up of two kinds of cells. � These are the body cells and the sex cells. � The body cells are called the somatic cells. � The somatic cells make up every part of your body for example the cells making up the bone. � The sex cells are called the gametes. � There are two types of gametes. � These are the sperm cells and ovum.

TERMINOLOGY: TERM: Somatic cells DEFINITION: USE IN SENTENCE: are body cells Skin cells are examples of somatic cells

TERMINOLOGY: TERM: Gametes DEFINITION: USE IN SENTENCE: are sex cells. Sperms and eggs are examples of gametes

INTRODUCTION � Cell division occurs in the somatic cells and in the formation of the gametes. � The cell that undergoes cell division is called the mother cell. � The new cells that are formed after cell division are called the daughter cells. � There � These a. b. are two types of cell division. are: Mitosis and Meiosis

INTRODUCTION � � � Mitosis is the type of cell division that occurs in somatic cells. It is simply when one cell divides and form two cells. Remember the new cells that are formed are called the daughter cells. The daughter cells are identical to each other and the mother cell is every way. The chromosomal number stays the same during mitosis.

TERMINOLOGY: TERM: Mitosis DEFINITION: USE IN SENTENCE: is the type of cell division Mitosis produces new cells that occurs in somatic cells, for growth, repair and when one cell divides and replacement form two identical cells

INTRODUCTION meiosis the mother cell divides twice to form 4 different daughter cells. � During � Each daughter cell has half the number of chromosomes as the mother cell. � For example if the mother cell had 46 chromosomes then after meiosis each daughter cell would have 23 chromosomes. � Meiosis occurs to form gametes.

THE CELL CYCLE � The cell cycle is also known as the cell division cycle. � The cell cycle takes place within a cell, it is the series of events that occurs when a cell divides and duplicate. � In eukaryotic cells, cell division occurs in 2 periods. � These are interphase and mitosis and cytokinesis.

THE CELL CYCLE interphase the cell grows by making proteins and organelles. � During � Also � The during interphase the DNA duplicates. collects nutrients cell also that are needed for mitosis during interphase. � During the mitosis phase the mother cell divides to from two identical daughter cells. � Mitosis is very important because it can allow a single cell to develop into a multicellular organism.

THE CELL CYCLE � From the diagram alongside you can see that most of the time of the cell cycle is taken up by interphase. � You can also see that mitosis and cytokinesis Time Allocation of each phase only takes up about 10% of the cell cycle.

MITOSIS � As mentioned earlier mitosis is the process by which one cell divides to form two identical daughter cells. � These identical daughter cells have the same number and type of chromosomes. � Cells that have the same number and kind of chromosomes are said to be genetically alike. � Remember that all the cells in the human body are genetically alike except for the sex cells.

MITOSIS-GENETICALLY IDENTICAL What exactly does genetically identical mean? � DNA is made up of small parts that controls or carries the genetic code for one or more characteristics or functions. � This � DNA portion of DNA is called a gene. contains the code for the appearance and function of many parts. Like eye colour, or the type of protein to be made.

MITOSIS-GENETICALLY IDENTICAL � People do not have the same DNA. However parts of their DNA may be similar to their parents or grandparents. �Remember! Identical twins have the same DNA!

MITOSIS- THE PROCESS � Mitosis is a type of cell division. � The actual process of mitosis is made up of two parts. � These two are the division of the… a. Nucleus b. Cytoplasm. � The nucleus divides first and the cytoplasm divides. � Now lets look at the division of the nucleus in an animal cell.

MITOSIS- THE PROCESS INTERPHASE: � This is preparation for nuclear division. � The DNA undergoes replication so that the genetic material in the chromatin material is doubled. Interphase

MITOSIS- THE PROCESS � The diagram alongside shows a micrograph of Interphase. Micrograph of Interphase

MITOSIS- THE PROCESS PROPHASE: � The chromatin network unwinds to form the single chromosomes. � The nuclear membrane and nucleolus start to disappear. � The centrioles move to the opposite poles.

MITOSIS- THE PROCESS � Study the micrograph of prophase. Micrograph of Prophase

MITOSIS- THE PROCESS METAPHASE: centrioles � During metaphase the chromosomes are found at the equator of the cell. � They occur in a single row. � They are attached to spindle fibers. Spindle fibers

MITOSIS- THE PROCESS ANAPHASE: � The spindle fibers shorten and the chromatids are pulled apart. � The chromatids are pulled towards the opposite end of the cell, towards the poles. � Each chromatid is a single stranded chromosome. Can you explain why this is the case?

MITOSIS- THE PROCESS � The micrograph alongside is of anaphase Micrograph of Anaphase

SOLUTION � Each chromatid is considered to be a single chromosome and the DNA underwent replication before the start of the division.

MITOSIS- THE PROCESS TELOPHASE: � There are now two groups of chromosomes at each pole of the cell. � The nuclear membrane and nucleolus reappear. � Now the cell has two nuclei with the same number and kind of chromosome as the mother cell.

MITOSIS- THE PROCESS � Study the micrograph alongside, carefully.

MITOSIS- THE PROCESS CYTOKINESIS: In animal cells Cytokinesis is the division of the cytoplasm. � It occurs once two new nuclei are formed. � In animal cells the cell membrane constricts. � The constriction eventually meet in the middle forming two new cells. �

MITOSIS- THE PROCESS CYTOKINESIS: In plant cell � A cell plate forms between the two new nuclei. � The cell plate divides the cell into two new identical cells. Cell plate Cytokinesis

TERMINOLOGY: TERM: Cytokinesis DEFINITION: USE IN SENTENCE: is the division of the cytoplasm Cytokinesis occurs differently in plant and animal cells

MITOSIS IN PLANT AND ANIMAL CELLS � There are difference in how mitosis occurs in plant and animal cells. � The table in the next slide discusses some of these differences.

MITOSIS IN PLANT AND ANIMAL CELLS � Differences cells. in mitosis between Plant and Animal ANIMAL CELL PLANT CELL 1. Centrosome forms spindle fibers during prophase. 1. Cytoplasm forms the spindle fibers during prophase. 2. Constriction of the cytoplasm occurs during cytokinesis 2. Cell plates are formed in the equatorial parts of the cell during cytokinesis

IMPORTANCE OF MITOSIS � From the above discussion you now know that mitosis results in the formation of identical cells. � This is extremely important in the growth of an organism, because in order to grow the organism would need a large number of identical cells. � Therefore it is mitosis that makes it possible for the unicellular zygote to grow into a multicellular organism by providing a large number of identical cells.

IMPORTANCE OF MITOSIS � Some unicellular organisms, such as the Amoeba, undergo a type of reproduction called binary fission. � During this process one cell simply divides to form two new cells that are identical to each other and the original cell. � From the above statement it is clear that binary fission is actually mitosis. � In spore producing organisms such as fungi, moss and fern, asexual reproduction occurs by mitosis.

IMPORTANCE OF MITOSIS � When cells naturally wear off they need to be replaced. Mitosis produces the identical cells that are needed to replace these lost cells. � When tissues are accidentally damaged they need to be repaired, once again mitosis provides the identical cells that make the repair possible.

IMPORTANCE OF MITOSIS � The importance of mitosis can be summarized as follows: a) Formation of new cells that may be used for growth, replacement and repair. b) Allows for asexual and vegetative reproduction.

SOMETHING FOR YOU TO DO Study the micrograph below and answer the questions that follow: A

SOMETHING FOR YOU TO DO 1. 2. 3. 4. 5. Name the phase shown. Give one visible reason for your answer. Name the phase that comes before this. Identify label A. Draw a diagram of the phase that follows the one shown.

SOLUTION: 1. 2. 3. 4. 5. Anaphase The chromatids are moving to the opposite poles. Metaphase. Chromatin. Your teacher will provide you with a labelled diagram.

CANCER-UNCONTROLLED CELL DIVISION AND GROWTH � Usually after mitosis has occurred some of the cells undergo structural and chemical changes so that they can perform specific functions. � These cells are said to be differentiated or specialized. � When these differentiated cells come together to perform a single function a tissue is formed. � These differentiated or specialized cells can no longer divide by mitosis.

CANCER-UNCONTROLLED CELL DIVISION AND GROWTH � Some cells however do not differentiate, they continue to divide in an uncontrolled manner. � Sometimes even the specialized cells begin to undifferentiate and continue to divide by mitosis. These cells become simplified again. � This continual and uncontrolled division of cells results in the formation of swellings or growths in various parts of the body. � These growths or swellings are called tumors.

TERMINOLOGY: TERM: Tumors DEFINITION: USE IN SENTENCE: Tumors: are growths or swellings that may or may not be cancerous Remember that a tumour may not be cancerous.

CANCER-UNCONTROLLED CELL DIVISION AND GROWTH � Two types of tumors maybe formed. � They are: a) Benign tumors and b) Malignant tumors. Benign tumors � These tumors stop growing. � They occur in small groups. � They do not invade the most important organs of the body. � They are not cancerous.

TERMINOLOGY: TERM: Benign tumors DEFINITION: USE IN SENTENCE: are tumors that are not cancerous. Benign tumours are not cancerous.

CANCER-UNCONTROLLED CELL DIVISION AND GROWTH Malignant tumors � Malignant tumors continue to grow. � They invade important organs. � Some of the cancer cells may break off and enter the blood or lymphatic system and are then carried to all parts of the body. � Therefore they are spread to even distant parts of the body. � They invade even the most distant parts of the body.

TERMINOLOGY: TERM: Malignant tumors DEFINITION: USE IN SENTENCE: are cancerous tumors Malignant tumours are cancerous tumours.

CANCER-CAUSES � The exact cause of the cell behavior is unknown. � Cancer causing agents have been identified by scientists. � These agents bring about cancer in certain people under certain conditions. � These cancer causing agents are called carcinogens.

CANCER-CAUSES � The carcinogens do not always cause cancer. � Some people are exposed to these carcinogen over a life time and never develop cancer while other people are exposed to these carcinogens for only a short period and develop cancer.

CANCER-CAUSES � Scientist believe that these people that develop cancer are predisposed to it. They have a weakness or susceptibility to the disease. � This weakness might be inherited. � It is important to know that cancer can not be inherited only the predisposition for cancer can be inherited. � But in very rare cases the actual cancer itself can be inherited.

CANCER � Here 1. 2. 3. 4. 5. 6. 7. 8. CARCINOGENS is a list of some of these carcinogens: Radiation (sun rays, x-rays, from atomic weapons) Smoking Hormonal imbalances Some processed foods Exposure to certain pollutants (for example industrial wastes, car exhaust fumes) Pesticides Viruses Constant and prolonged irritation (e. g. mouth cancer can be caused by pipe smoking.

TERMINOLOGY: TERM: Carcinogens DEFINITION: USE IN SENTENCE: are cancer causing agents are called carcinogens Carcinogens may not cause cancer in everyone.

TYPES OF CANCER � There are 3 types of cancer. � These 3 types of cancer are: 1. Carcinomas- affects the skin and epithelial tissues that line certain organs and glands. 2. Sarcomas- affects bone, cartilage and muscle tissue. 3. Leukemia- affects the blood and lymphatic system.

TREATMENT AND ‘CURE’ � Treatment includes radiation, chemotherapy, surgery, laser therapy and cryosurgery. a) Cryosurgery- extreme cold is applied to the tumor instead of a scalpel. The advantage is that very little bleeding occurs.

TREATMENT AND ‘CURE’ b) Surgery- is used if the cancer is identified in the early stages. Doctors remove the tumor surgically before it starts to spread to other parts of the body. Remember though that often the cancer cell break off and spread to other parts of the body before the surgery. Therefore the cancer may still exist in another part of the body.

TREATMENT AND ‘CURE’ c) Radiotherapy-here radiation is used to treat cancer. Radiation can be administered by machines, injections or planting radiation capsules within the body. d) Chemotherapy- involves the use of a combination of various chemicals. These chemicals either destroy the cancer cells directly or their DNA and thus preventing the cell from reproducing and spreading.

TREATMENT AND ‘CURE’ � Chemotherapy and radiation have harmful side effects. Which include vomiting and nausea. � Doctors do not speak of a cure for cancer. They speak of the percentage of the patients that are likely to be cancer-free for a specific time. The earlier the cancer is detected the more likely it is for the patient to remain disease free.

BELIEFS AND ATTITUDES CONCERNING CANCER 1. 2. Fear of the disease: many people fear the disease. They worry about the treatment and the time they need to take off work for the treatment. Women who have breast or cervical cancer feel that they have lost their femininity and reproductive value. Uncertainty of the effectiveness of the treatment of the cancer: many people rather not know because they believe that there is no hope and they will die anyway.

BELIEFS AND ATTITUDES CONCERNING CANCER 3. Reluctance of men to ask for help: apart from skin cancer the most common type of cancer among men is prostate cancer. Despite this men are not eager to go for prostate cancer testing. Many believe that this is due the reluctance of men to ask for help or the belief that a cancer diagnosis will reduce other people’s opinion of them.

TERMINOLOGY: �Somatic cells: are body cells. � Gametes: are sex cells. � Mitosis: is the type of cell division that occurs in somatic cells, when one cell divides and form two identical cells. � Interphase: is preparation for nuclear division � Cytokinesis: is the division of the cytoplasm. � Tumors: are growths or swellings that may or may not be cancerous.

TERMINOLOGY Benign tumors: are tumors that are not cancerous. � Malignant tumors: are cancerous tumors � Carcinogens: are cancer causing agents are called carcinogens. �

QUESTION 1 1. During mitosis the chromosomal number is… A. Halved B. Doubled C. Stays the same D. None of the above.

QUESTION 2 2. At the end of mitosis the chromatin material is… A. Different B. The same C. Doubled D. Both A and C

QUESTION 3 3. Mitosis occurs in… A. Bone cells B. Formation of sperms C. Both A and B D. None of the above

QUESTION 4 4. During cytokinesis in a plant cell a____ is formed. A. Cell plate B. Cleavage furrow C. Spindle fibers D. Chromatid

QUESTION 5 5. Spindle fibers are… A. Formed by the centrioles and found in plant cells only B. Formed by the centrioles and found in animal cells only C. Formed by the centrioles and found in both plant and animal cells D. Formed by the centrioles and found in neither plant cells or animal cells.

QUESTION 6 6. During metaphase the chromatids… A. Occur at the equator B. Occur at the poles C. Occur as the chromatin network D. None of the above

QUESTION 7 7. If the human cell has 46 chromosome in it nucleus at the end of mitosis it will have… A. 46 chromosomes B. 23 chromosomes C. 92 chromosomes D. No chromosomes

QUESTION 8 8. During anaphase the chromatids… A. Have moved to the poles B. Are at the equator C. Are moving to the poles D. None of the above

QUESTION 9 9. A malignant tumor… A. Can spread and is cancerous. B. Cannot spread and is cancerous. C. Can spread and is not cancerous. D. Cannot spread and is cancerous.

QUESTION 10 10. Treatment for cancer is… A. Cryosurgery B. Radiotherapy C. Both A and B D. None of the above

QUESTION 11 11. Cytokinesis occurs… A. Before nuclear division B. After nuclear division C. During prophase D. During interphase

QUESTION 12 12. The preparation for cell division is called… A. Interphase B. Prophase C. Metaphase D. Cytokinesis

QUESTION 13 13. The chromosomes line themselves at the equator during… A. Interphase B. Prophase C. Metaphase D. Cytokinesis

QUESTION 14 14. The phase that comes after prophase is… A. Interphase B. Prophase C. Metaphase D. Cytokinesis

QUESTION 15 15. The division of the cytoplasm is known as… A. Interphase B. Prophase C. Metaphase D. Cytokinesis

QUESTION 16 16. The final phase of nuclear division is… A. Interphase B. Prophase C. Metaphase D. Telophase

QUESTION 17 17. The chromatin network unwinds during… A. Interphase B. Prophase C. Metaphase D. Telophase

QUESTION 18 18. The spindle fibers shorten during… A. Anaphase B. Prophase C. Metaphase D. Telophase

QUESTION 19 19. The correct of the events of mitosis is: A. Prophase, metaphase, anaphase, telophase B. Telophase, anaphase, prophase, interphase C. Metaphase, telophase, interphase, prophase D. Prophase, anaphase, metaphase, telophase.

QUESTION 20 20. DNA replication occurs during… A. Interphase B. Prophase C. Metaphase D. Telophase

SOLUTION 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. C B A A C A C 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. B A C C D D B A A A