Cell Divison

• The Cell Cycle


  • The life cycle of a cell begins when a cell is first created and ends when the cell is ready to divide
  • The three phases of the Cell Cycle are: Interphase (preparation phase), Mitosis (active division), Cytokinesis (cytoplasm splits; two distinct cells separate)
• Determine if each statement below is an example of GROWTH, REPAIR or REPRODUCTION
• Let’s Practice!

  • A red blood cell is produced to replace one that is dying: repair
  • A bacterium divides in half to produce a new bacterium: reproduction
  • You are taller than you were last year: growth
  • A new bone cell is produced to begin healing a crack in a bone: repair
  • Your fingernails get longer over the period of a month: growth
  • Your skin reforms following peeling from a sunburn: repair
  • A newborn baby gains 3 lbs in its first 2 months of life: growth
• Reproductive Cells

  Cells specialized for sexual reproduction
• Cells which are specialized for sexual reproduction are known as gametes
• Phases of The Cell Cycle

  1. Uncondensed DNA = chromatin

  2. Condensed DNA = chromosome

  3. Interphase: cell is carrying out life functions, DNA is visible as chromatin, DNA makes a copy of itself = replication

  4. Prophase: nuclear membrane begins to disintegrate, DNA condenses into chromosomes, centrioles migrate to poles of cell, spindle fibers appear and attach to centromeres

  5. Metaphase: chromosome pairs line up along the equator of the cell

  6. Anaphase: chromosomes split apart and a full set moves to each new cell, looks like a tug of war

  7. Telophase: nuclear membrane reforms around chromosomes; cell starts to pull apart

  8. Cytokinesis: cytoplasm pinches in and divides in half, two new daughter cells are produced
• Cells which are specialized for sexual reproduction are known as
• Gametes contain half the number of chromosomes as the body cells, so are referred to as haploid
• Somatic cells are referred to as diploid
• Human gametes contain
• Human gametes

  • Male- sperm
  • Female- egg
• Meiosis


  A type of cell division resulting in the production of gametes (sperm and eggs), which have half the number of chromosomes as somatic cells
• Meiosis only occurs in organs called gonads
• Reproductive organs
• Reproductive organs


  • Males- testes (where sperm cells are made)
  • Females- ovaries (where egg cells are made)
• Fertilization - the combining of the sperm and the egg to form a zygote
• Meiosis proceeds through the Cell Cycle twice EXCEPT: the second time, so the chromosomes do not replicate
• Meiosis results in 4 haploid daughter cells
• Each daughter cell will contain half the number of chromosomes as the parent cell
• Mitosis occurs in

  unicellular organisms
• Meiosis occurs in


  organisms that carry out sexual reproduction (mostly multicellular)
• Mitosis produces 2 daughter cells
• Meiosis makes the gametes necessary for sexual reproduction
• Comparing Mitosis and Meiosis
• Comparing Mitosis and Meiosis

  • Occurrence
  • Number of daughter cells produced
  • Characteristics of daughter cells
  • Purpose
• This is a sketch of Mitosis

  
• This is a sketch of Meiosis

  
• Living cells give rise to the same type of living cells for the purposes of growth, repair, and reproduction
• Cells reproduce by dividing in half, and distributing equal amounts of cytoplasm and DNA to each new cell. This is called cell division
• In mitosis, one parent cell generates two new daughter cells, which are identical to itself. These cells are described as "diploid" cells. In meiosis, one parent cell generates four new daughter cells, which are called “haploid” cells due to it having half of the parent‘s chromosomes.
• Mitosis


  The process of cell division that results in the production of somatic cells and are described as diploid
• Mitosis is how some organisms reproduce (mostly unicellular)
• Since only one parent is needed, it is called asexual reproduction