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Chapter 3 Heredity and Variation

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Chapter 3 Heredity and Variation

  1. 1. CHAPTER 3 HEREDITY AND VARIATION
  2. 2. 3.1 CELL DIVISION •Human beings have 46 chromosomes. •Chromosomes are located in the nucleus. •Chromosomes consists of DNA and proteins. •Gene carry genetic information's.
  3. 3. CELL DIVISION (PEMBAHAGIAN SEL)  There are two types of cell division: Cell division Mitosis Meiosis * Somatic cell (other than reproductive cell) * Produces 2 daughter cells * Reproductive cell (sperm and ovum) * Produces 4 daughter cells
  4. 4. MITOSIS Chromosome shorten and thicken •Replication of chromosome •Chromosomes align at the centre of the cell •The nucleus membrane disappears •Chromatids separate and move to the opposite •The cell starts to divide •The nucleus membrane forms. •2 daughter cells •Same number of chromosomes
  5. 5. MITOSIS UNDER MICROSCOPE
  6. 6. IMPORTANCE OF MITOSIS Produce new cells for growth and to replace damaged cells  Ensures the number of chromosomes in the daughter cell is the same as that of the parent cell 
  7. 7. MEIOSIS Replication and crossing over •Half number of chromosomes Produces 4 daughter cells
  8. 8. MEIOSIS UNDER MICROSCOPE
  9. 9. IMPORTANCE OF MEIOSIS To produce gametes/reproductive cells (sperm or ovum)  Allows for genetic variations among the same species 

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