Biology Paper 1

• What structures contain chromosomes in eukaryotic cells?

  Nucleus
• What are chromosomes made from?

  Highly coiled strands of DNA
• How many chromosomes do diploid organisms have in pairs?

  Normally found in pairs
• From whom do organisms inherit their chromosomes?

  One from each parent
• How many chromosomes do humans have?

  46 chromosomes
• How many pairs of chromosomes do humans have?

  23 pairs
• How many chromosomes do horses have?

  64 chromosomes
• What is the exception regarding red blood cells and chromosomes?

  They lose their nuclei and have no chromosomes
• What must happen to genetic material before a cell divides?

  It needs to be doubled
• What shape do chromosomes take when a cell prepares to divide?

  X-shaped

  
• What happens to chromosomes when a cell is not dividing?

  They are usually uncoiled
• What is mitosis?

  A stage in the cell cycle when the nucleus divides
• What occurs during the growth phase of the cell cycle?

  Genetic material is doubled
• What are chromatids?

  Strands of replicated chromosomes
• What happens to chromatids during mitosis?

  They are separated and pulled apart

  
• What forms around each new group of chromosomes after mitosis?

  A new nucleus

  
• What is cytokinesis?

  Division of cytoplasm and cell membrane
• Why is mitosis important for multicellular organisms?

  It produces two identical daughter cells

  
• What happens when a sperm cell fertilizes an egg cell?

  A zygote cell forms and divides by mitosis
• What is the role of mitosis in embryo development?

  Cells divide to form an embryo

  
• What are the three overall stages of the cell cycle?

  Growth phase, mitosis, cytokinesis
• How can you identify cells that are not actively dividing?

  Chromosomes will be unraveled and non-distinct
• What are specialized cells?

  Cells with a specific structure for a function
• How many specialized cell types are in the human body?

  About 250 specialized cell types
• What happens to specialized cells that divide by mitosis?

  They produce the same type of specialized cell
• What are stem cells?

  Undifferentiated cells capable of division
• What is the role of embryonic stem cells?

  To form different tissues and organs
• What do adult stem cells primarily do?

  Replace lost cells and produce new cells
• What are meristem cells in plants?

  Unspecialized cells that can differentiate
• What can meristem cells in roots differentiate into?

  Root hair cells and other cells
• How can stem cells be used in medicine?

  To repair damaged organs and tissues
• What is therapeutic cloning?

  Producing an embryo with the patient's genes
• Why are stem cells from therapeutic cloning not rejected?

  They have the same genes as the patient
• What is a benefit of cloning rare plant species?

  To protect them and maintain biodiversity
• What is a potential environmental benefit of cloning crop plants?

  Reduces need for pesticides
• What are the key differences between embryonic and adult stem cells?

  • Embryonic stem cells can differentiate into most cell types.
  • Adult stem cells are limited to specific types (e.g., blood cells).
  • Embryonic stem cells are derived from early embryos.
  • Adult stem cells are found in mature tissues.
• What are the stages of the cell cycle?

  1. Growth phase: Chromosome doubling and increase in subcellular structures.
  2. Mitosis: Division of the nucleus.
  3. Cytokinesis: Division of cytoplasm and cell membrane.
• What are the roles of stem cells in animals and plants?

  • Animals:
  • Embryonic stem cells form tissues and organs.
  • Adult stem cells replace damaged cells.
  • Plants:
  • Meristem cells differentiate into various plant cells.
• What are the advantages and disadvantages of using stem cells in medicine?

  Advantages:

  • Potential to cure diseases.
  • Can replace damaged tissues.

  Disadvantages:

  • Ethical concerns with embryonic stem cells.
  • Risk of rejection in transplants.