Lecture 5 - Asexual (mitosis) reproduction

• Cell Theory

  • All living things are composed of one or more cells
  • The cell is the smallest entity that retains the property of life
  • New cells arise only from cells that already exist
• You have about 100 trillion cells in your body. They all came from a single fertilized egg (zygote) which divides many times. 

  Each time a cell divides all of its genetic information (DNA) and its organelles must be doubled. 
• A cell spends most of its time in Interphase. During this time the cell:

  • Rapid Growth: Grows to its full size
  • Function: Performs its specific function
  • Doubling DNA: Doubles its DNA to prepare for cell division
• The Process of cell division itself takes a relatively short period of time. Cell division that results in the production of genetically identical daughter cells is called mitosis and is followed by cytokinesis.
• Interphase

  • G 1 Phase (Cell Growth) ~ cell is actively performing its function and is increasing in size.
• Interphase

  • S Phase (DNA Replication) ~ A copy of a DNA molecule is produced so that when mitosis occurs, both daughter cells can receive a complete set of instructions.
• Interphase

  • G 2 Phase (Preparation for mitosis) ~ the cell is approaching its maximum size and is beginning its final preparation for cell division. 
• Mitosis

  • Occurs in all body cells except sex cells.
  • The cell divides and produces 2 genetically identical cells.
  • 4 stages: Prophase, Metaphase, Anaphase, & Telophase
• Prophase

  • DNA becomes compact and becomes visible, thus becoming Chromosomes.
  • Each chromosome has two strands called sister chromatids.
  • Nuclear membrane breaks down.
  • Centrioles move to poles of the cell.
  • Spindle fibers will attach to the centromere on the chromosome.
• What is this?

  A) Prophase

  
• Label

  A) Centromere

  B) Sister

  C) Chromatid

  
• Metaphase

  • Chromosomes line up at the middle of the cell. Being pushed by the Spindle Fibers
  • You can see this actually happening!
• What is this?

  A) Metaphase

  
• Anaphase 

  • Chromosomes will be separated by sister chromatids. They are pulled apart at centromere producing 2 single stranded chromosomes.
  • Each separate chromosome is pulled to the opposite pole by the Spindle Fibers towards the centrioles.
  • A complete set of chromosomes end up at each pole. 
• What is this?

  A) Anaphase

  
• Telophase

  • Chromosomes reach the opposite poles of the cell and begin to stretch out again so you no longer can see them. 
  • Nuclear membrane forms around each mass of chromosomes.
• What is this?

  A) Telophase

  
• Cytokinesis

  • Cytoplasm divides and one centriole will go to each cell
  • This is the end of cell division
  • Two daughter cells re-enter the Interphase stage. 
• Cell Differentiation

  • Cells have the ability to differentiate into different types of cells.
  • Cells can become nerve cells, hair cells, liver cells etc. Each one has its own function, shape and structure.
• • Different cell types will have greater/fewer of certain organelles depending on the function of the cell.
• • Specialized cells have physical and chemical differences to help them perform one job very well.
• • Every multicellular organism started off as one single cell. This single cell continues to divide and then the cells begin to show differences and become specialized. 
• • The process that produces specialized cells is called Cellular Differentiation.
  • Cellular Differentiation is directed by the genetic information inside the cell. 
• • Once a cell has “specialized” it will only be able to divide and produce the same type of cell. 
  • For example: a liver cell can only produce a liver cell
  • However, some cells in your body have the amazing ability to turn into anything!...  these are called stem cells (there are two types in your body)
• 2 Types of Stem Cells

  • Embryonic Stem Cells - Cells that come from Embryonic Cord blood and fetus cells.
  • Tissue Stem Cells - Cells from tissues and can only differentiate into certain types of cells.

  1. Example: Cells in Bone Marrow can differentiate into red blood cells, white blood cells, or platelets
• Just as a whole organism has a lifespan, so do cells. The cell cycle describes the lifespan of a cell.

  A) Parent cell

  B) DNA is doubled

  C) Cell division

  D) 2 identical daughter cells