Cell Division and Stem Cells

• What do most cells in your body contain?

  Nucleus
• What does the nucleus contain?

  Genetic material in the form of a chromosome
• What are chromosomes?

  Coiled up length of DNA molecules and each one carries a large number of genes
• What does each gene control?

  The development of different characteristics e.g hair colour
• Body cells contain?


  Two copies of each chromosome one from the organism mother and the other it’s father
• Sex chromosomes of a male

  XY
• Sex chromosomes of a female

  XX
• Chromosomes

  Humans have 23 pairs of chromosomes (46 in total) found within each cell containing a nucleus
• Which part of the cell contains genes and chromosomes?

  Nucleus
• Which chemical are genes and chromosomes made of ?

  DNA
• How many chromosomes are found in human body cells ?

  23 pairs (46 in total)
• What does DNA stand for?

  Deoxyribonucleic acid
• Do all living organism have equal quantities of chromosomes?

  No
• A cell divides when:

  • An organism grows
  • organism need to replace worn out cell
  • organism need to repair damages tissue
• What is Mitosis?

  Is a type of cell division which ensures that, when a cell divides each new cell produced has the same genetic information
• During the process of mitosis?


  All the chromosomes and genes in the mother cell are copied. The cell divides to produce two daughter cell. The daughter cell are genetically identical to each other and to the mother cell. The number of chromosomes stays the same
• Diagram of mitosis


  Diagram

  
• What is mitosis involved in?

  Cell division
• How many daughter cells are produced?

  2
• How do the daughter cells compare to each other?

  Genetically identical
• Give 3 reasons why an organism must undergo mitosis?

  1. Organism grows
  2. Replace worn out cells
  3. Repair damaged tissue
• What happens when cells become cancerous?

  Uncontrolled growth. And new cells are produced even if the body does not need them
• What is a group of cancerous cells produce a growth called?

  Tumour
• What causes cancer- Carcinogens 


  Substance capable of causing cancer. It may occur naturally in the environment or may be generated by humans
• What causes cancer - Lifestyle

  Smoking, your weight, your diet, how active you are, sun exposure and how much alcohol you drink
• What causes cancer- Industrial and environmental factors

  Chloride, Radon and Arsenic are examples of toxic substances that can increase the risk of cancer when people are exposed to them
• What is the cause of a tumour?

  Group of cells that grow and divide uncontrollably
• Meiosis

  Two parents are needed in sexual reproduction’s. During this process the nucleus of a male gamete fuses with the nucleus of a female gamete producing a new cell called zygote
• How many chromosomes are in humans?

  Each gamete contains 23 chromosome, half the number found in the other cells of the body.
• What happens when the male and female fuses?

  They become zygote which will turn become a new embryo containing the full 46 chromosomes- half from the father and half from the mother
• What is the fusion of gametes called

  Fertilisation
• What are gametes formed by?


  Meiosis
• In animals what are the gametes?

  Egg and sperm
• In flowering plants what are the gametes called?

  Pollen and eggs
• Process of meiosis 


  Copies of the genetic information are made, the cell divides twice to form four gametes each with a single set of chromosomes known as haploid cells. All gametes are genetically different from each other they show variation
• Meiosis 


  Diagram

  
• What is meiosis involved in?

  Production of gametes
• How many daughter cells are produced in meiosis?

  4
• How do the daughter cells compare to each other?

  Genetically different
• Why do organisms undergo meiosis?

  For reproduction