Cell Growth

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Cell Growth ReproductionMITOSIS
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Cell Growth

• When a living thing grows it does so by producing
  more cells INSTEAD of making the cells it has
  larger
• Whether it be elephant, human, jellyfish or
  earthworm all the cells are about the same size
• There are two reasons why this happens
• DNA Overload
• Exchange of Materials

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DNA Overload

• All the information to run a cell is located in
  the nucleus as a code of DNA
• If the cell were to get bigger and bigger there
  would not be enough information to run the
  whole cell

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Why are cells so small?

• Cells are surrounded by their cell membrane.
• Through that membrane the cell must transport
  everything they need (aka food wastes).
• If there isnt enough membrane space, cells cant
  get or get rid of what they need.
• So there must be a balance between surface area
  (room to move stuff in out)
• and volume (stuff)

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Reproduction Not as simple as it looks.
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First things first Why must cells divide?

• ALL CELLS COME FROM OLD CELLS!
• Cant get anything new without working with what
  you already have!
• 3 Major Reasons Cells Divide
• Growth you start as one cell
• Development you get bigger, learn change
• Repair your cells get worn out

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What does a cell need to survive?

• A FULL set of genetic material (DNA or RNA)
• Biggest hurdle to cell division is making sure
  each cell transfers ALL the DNA when it makes new
  cells
• This gets more difficult as there becomes more
  DNA to transfer

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one bit of genetic information
I
II
III
IV
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one bit of genetic information
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To Prevent Mistakes CHROMOSOMES!

• Putting all the DNA into neat packages (called
  chromosomes) helps jump this hurdle
• Chromosomes in red

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Parts of a Chromosome

• Chromosome whole thing
• Sister Chromatid each
• arm of chromosome
• Centromere middle,
• Connects chromatids
• LABEL YOUR CHROMOSOME

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Chromosome Terms

• Un-replicated Replicated

Whole thing Homologous Chromosome
Sister Chromatid (as long as theyre attached)
Arm
Centromere (where theyre attached
Centromere
Sister Chromatid
Arm
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A Cells Life

• A cells life can be divided into 2 stages
• Interphase (3 Parts) Non-dividing stages
• Gap 1 (G1)
• Growth phase 1 cells get bigger
• Most cells are found in this phase Normal
  Cells
• Synthesis (S)
• New DNA is synthesized, or made
• Gap 2 (G2)
• Growth phase 2
• Preparations for division are made
• Mitosis (4 parts) Dividing stages
• Prophase
• Metaphase
• Anaphase
• Telophase

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So What is Mitosis? (My-toe-sis)

• It is the division of somatic cells
• Somatic non-reproducing, any cell thats not a
  sperm cell or an egg cell
• A single cell divides into TWO daughter cells
• These two cells are identical they have they
  SAME DNA
• Basically, like a cell copy machine
• For convenience, we break the process down into 4
  stages. But, really is a continuous process.

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Cell Cycle Interphase

• Interesting things happen
• Cells preparing to divide
• Genetic material doubles
• The cell is doing what it normally does

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Now on to division MITOSIS

• Prophase
• Chromosomes pair up.
• Chromosomes thicken become visible chromatids
  are joined by centromere
• Centrioles move to opposite ends of cell
• Nucleolus disappears
• Nuclear membrane dissolves

DNA Chromatin condenses to Chromosomes
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Now on to division MITOSIS

• Metaphase
• Chromosomes meet in the middle
• Chromosomes line
• up at equator aka the
• metaphase plate
• Chromosomes
• attached to spindle
• fibers (from centrioles)
• at centromeres

DNA Homologous Chromosomes are in pairs of
sister chromatids
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Now on to division MITOSIS

• Anaphase
• Chromosomes get pulled apart
• Spindle fibers shorten and pull sister chromatids
  to the opposite ends of the cell

DNA Sister chromatids separate into daughter
chromosomes
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Now on to division MITOSIS
DNA Chromosomes de-condense back to chromatin

• Telophase
• Now there are two!
• Chromosomes de-condense
• Spindle fibers disintegrate
• Nuclear membrane forms
• And the cell (finally) divides aka CYTOKINESIS

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Now on to division MITOSIS

• Cytokinesis
• Cutting of cell membrane
• Different in plants and animals
• Animals
• Cell membrane simply pinches (on cleavage furrow)
  until it splits cell
• Plants
• Because of Cell Wall, cant pinch. Instead, cell
  grows a cell plate in middle of cell until it
  connects to sides of wall

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Onion Root Tip
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Interphase Prophase

Return to index of articles by students on the
'Principles and techniques of photomacrography'
course, November 2004,Biomedical Photographic
Communications (BPC) program at the Rochester
Institute of Technology (RIT). Article hosted
on Micscape Magazine (Microscopy-UK).

   
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Metaphase Anaphase
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Telophase Interphase
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http//www.sciencemag.org/content/vol300/issue5616
/images/data/91/DC1/1082177S10.mov
Paste the link above and choose Movie S10 at
the bottom of the page
http//www.bio.davidson.edu/misc/movies/mitosislil
y.mov
Paste the link above and choose Movies of Cells
Movies of Plants Movies of Animals
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This is a complicated process what happens when
things go wrong?

• There are several factors that try to control the
  cell cycle
• Before a cell divides the DNA is checked to make
  sure it was replicated correctly
• Chemical signals tell a cell when to start and
  stop dividing
• http//www.cancerquest.org/index.cfm?page193
• Cells also communicate to neighboring cells to
  tell them to stop growing
• http//www.cancerquest.org/index.cfm?page2463

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This is a complicated process what happens when
things go wrong?

• CANCER

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Cancer is a disease of the cell cycle. Some of
the bodys cells divide uncontrollably and tumors
form.

• Tumors in Liver

• Tumor in Colon

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