Cell Reproduction - Download as PowerPoint

							             Cell Growth
• As living things grow, they produce more
  & more cells.

• Cells are about the same size in almost all
  organisms.
      Limits to Cell Growth
• Surface Area
  – The total area of the cell membrane


• Volume
  – The space within the cell
    • cytoplasm, organelles, & nucleus
       Surface Area = LxWx6
       and Volume = LxWxH

                               2
        1
   1                       2
S.A.= 6 cm2          S.A.= 24 cm2      (4x’s)
Vol = 1cm3           Vol = 8 cm3       (8x’s)


       As a cell grows, Volume .

 Surface Area  too BUT not as much.
               Cell Growth
• If S.A. & Volume increase at different
  rates, the cell will have difficulty getting O2
  & nutrients & removing waste.

• The cell will become less efficient at
  performing its functions.

• Therefore, cells divide before they get too
  large.
Chapter 8
               Chromosomes
• Chromosomes are structures in the
  nucleus that contain our DNA.
  – ‘chromo’ colored & ‘somes’ bodies


• Every organism has a specific number of
  chromosomes
    •   Fruit flies = 8
    •   Lettuce = 18
    •   Humans = 46
    •   Primates = 48
    •   Dogs = 78
      Chromosomes cont’d
• You get ½ (half) of your 46 chromosomes
  from each parent.

• They pair together based on similar size &
  shape & are called Homologous.

• These homologous chromosomes have
  genes that express similar traits.

• Genes – a segment on a chromosome.
      Chromosomes cont’d
• Cells with 2 sets of chromosomes (from
  each parent) are called Diploid.
  – Example: body cells (contain 46
    chromosomes)


• Cells with only 1 set of chromosomes are
  called Haploid.
  – Example: sperm & egg cells (contain 23
    chromosomes)
            The Cell Cycle
• The cell cycle is a series of events that
  takes place from one cell division to the
  next.
• This cycle consists of growth &
  development, division, & death of a cell.
             Cell Division
• Mitosis is the process in which a body cell
  divides & produces 2 (two) new identical
  cells (called daughter cells).

• Every cell in your body has a nucleus with
  46 chromosomes (except sperm or egg cells)

• Mitosis allows growth & replaces worn-out
  or damaged cells.
                 Interphase
• Period between cell
  division.

• Most of a cell’s life is
  spent in Interphase
  (growing & functioning)

• DNA Replication: Cells
  duplicate chromosomes
  to prepare for cell
  division.
                 Prophase
• Nucleolus & nuclear
  membrane
  disappear.

• Centrioles move to
  opposite ends of the
  cell.

• Spindle fibers form.
              Metaphase
• Chromosomes meet-
  up in the middle of
  the cell.
               Anaphase
• Chromosomes split apart
  at the centromere (or
  center).

• Chromatids (1/2 of a
  chromosome) separate &
  move apart to opposite
  ends of the cell.
                   Telophase
• New nucleus forms.

• Cytokinesis: the
  cytoplasm divides forming
  2 new cells

• Two new cells form.
  – Parent Cell: the original cell.
  – Daughter Cells: the new
    cells.
 How to Remember Mitosis?!
Interphase     I’ve       In-between
Prophase       Probably   Prepare
Metaphase      Mixed      Meet
Anaphase       All        Apart
Telophase      This       Tear
back up top   up
           Mitosis Review
Purpose:
• To produce 2 daughter cells that are
  identical copies of the parent cell.
           &
• To maintain the correct number of
  chromosomes from cell to cell.
        Sexual Reproduction
Sexual Reproduction:
When sperm & egg
  from 2 parents join
  together to produce a
  new organism.

Each parent contributes
  half (½) of their
  chromosomes to their
  offspring.
                 Meiosis
• The process that produces haploid sex
  cells (sperm & egg).

• Occurs in two stages.

• Meiosis is the driving force behind
  evolution ~ it results in genetic variation.
  Important Events in Meiosis:
• Synapsis: 2 sets of chromosomes line-up
  to form a tetrad (4 chromatids).

• This is followed by crossing-over, or the
  exchange of genes between
  chromosomes (from each parent).

• Results in recombination: a new mix of
  genetic info.
               Meiosis
           Males vs. Females

• Spermatogenesis – meiosis that produces
  sperm cells
   – 4 sperm cells are produced from 1 cell.
• Oogenesis – meiosis that produces an egg cell.
   – Different than sperm b/c only ONE egg is
     produced.
   – The other 3 cells, called polar bodies, get
     only a small amount of cytoplasm &
     eventually die.
             Other Terms
• Gametes: haploid sex cells (sperm/egg)
• Fertilization: the successful joining of
  gametes.
• Zygote: the new cell formed when a
  sperm fertilizes an egg.
  – male sperm + female egg = zygote
• Gonads: organs where gametes are
  produced.
  – Testes: male gonads
  – Ovaries: female gonads
         Mitosis vs. Meiosis

             MITOSIS         MEIOSIS
Occurs in -  body cells      sex cells
Produces - identical cells   gametes
cells form - diploid         haploid
      Asexual Reproduction
• Asexual Reproduction: when an new (&
  identical) organism is produced from 1 parent.

• Binary Fission: simplest form; cell spits in 2
  (unicellular organisms: prokaryotes, bacteria)

• Spores: Protective wall forms around
  chromosomes to create a spore.
  – When it leaves the parent cell, it can remain inactive
    until environmental conditions are favorable. Then it
    will start to germinate/grow. (Molds/Fungus
    reproduce this way)
• Budding: A small part of a cell pinches off to
  form a new cell. (yeast)


• Vegetative Propagation: Some plants
  produce new plants that are attached but
  eventually split-off.
   – Strawberries & potatoes (eyes) send out
     ‘runners’ or horizontal stems that take root &
     develop into new plants.


• Regeneration: Animals that have the ability
  to develop lost body parts or form new
  individuals from a single fragment. (starfish)