Mitosis and Cell Division

• The cell cycle involves cell growth and division, including mitosis, which allows for cell growth, repair, and asexual reproduction.

Interphase

• Initial growth phase
• Extra ribosomes, mitochondria, and other sub-cellular structures are produced.
• The cell's chromosomes (made of DNA) get replicated.

Mitosis

• Two sets of chromosomes are pulled to opposite ends of the cell
• The nucleus divides into two parts

Cytokinesis

• The cytoplasm and cell membranes divide
• Creates two identical diploid cells with two sets of chromosomes

Mitosis

• Chromosomes condense into a tight coil
• Chromosomes line up along the middle of the cell and are pulled to opposite ends
• The nucleus splits into two new nuclei during telophase
• Daughter cells have the same chromosomes as each other and the original parent cell
• Important for processes that require identical cells to be produced (e.g., growth and repair of tissues, asexual reproduction)

Plant Growth

• An increase in the size or number of cells (by mitosis)
• Causes an organism to get bigger
• Stages of growth happen in three different regions in plants:
  • Zone of cell division: Near the tip of a root where cells divide by mitosis and new cells are created
  • Zone of cell elongation: Further up the root next to the zone of cell division, where the cells grow in size
  • Zone of cell differentiation: Even further up the root, next to the zone of cell elongation, where the new cells differentiate and specialise into different types of cells

Cell Differentiation

• The process where a cell develops new sub-cellular structures to let it perform a specific function
• The cell becomes specialised
• Embryos: Cell division happens during an organism's development
  • Organisms start as one cell and these cells divide to form embryos that differentiate to produce cells that can perform all of the body's functions
• Plants: Many plants keep their ability to differentiate throughout their life
  • Able to create new tissues (matter that animals and plants are made from)
• Adult animals: Cell differentiation is rare in mature animals
  • Cells mostly divide to replace cells and repair tissues; new tissues are rarely created

Stem Cells

• Undifferentiated cells that have not yet specialised to perform a specific function
• Can create more stem cells or differentiate to perform another function
• Found in:
  • Embryos: Can differentiate into most cell types to produce all of the cell types that will make up the organism
  • Plant meristems: Can differentiate into all types of plant cell throughout the life of a plant, allowing the plant to grow for their whole lives
  • Bone marrow: Differentiate into fewer cell types than stem cells in embryos; used to replace dying cells and damaged tissues

Uses of Stem Cells

• Stem cell treatments: May be able to replace damaged cells
  • To replace the damaged cells that cause diabetes or paralysis
  • To treat patients with burn injuries, arthritis, and Parkinson's disease
• Therapeutic cloning: Produces an embryo with the same genes as the patient
  • Stem cells taken from this embryo will have the same DNA as the patient
  • Patient's body will not reject the stem cells or body cells made from the embryo's stem cells
  • This is ideal for use in stem cell medical treatments

Disadvantages of Stem Cells

• Viral infections: Stem cell transplantation could transfer viral infections
• Ethical beliefs: Some disagree with the use of stem cells on religious grounds
  • Believe that life begins at contraception, meaning that the embryo is alive
  • View the use of embryonic stem cells as killing an embryo
• Rejection: As with other organ transplants, introducing stem cells into a patient could cause the patient's immune system to reject and destroy the new cells.

Cell growth and division including interphase, mitosis, and cytokinesis. Mitosis allows for cell growth, repair, and asexual reproduction. Daughter cells have the same chromosomes as each other and the original parent cell.