Development

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Development

• by
• Mr. Charlton Ms. Hogan
• Lebanon High School

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DEVELOPMENT MATH IS EVERYWHERE

• DEVELOPMENT Growth Differentiation

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Components of Development

• Growth- The process of a multicellular organism
  increasing its number of cells, becoming larger.
  (i.e. zygote to an adult)
• Differentiation- The process of cells in a
  multicellular organism (initially all alike)
  becoming different from each other generating the
  various tissues (i.e. nerve, muscle, skin and
  bone, etc.) necessary to be a functional adult .

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Thoughts on developmentGrowth

• Cells generating more cells (Mitosis and
  Cytokinesis) (asexual reproduction)
• A single cell has size limits, (limited by
  physics) therefore for organisms to become larger
  they must be multicellular.
• All cells of an organism have a complete set of
  DNA to make the entire organism.
• Cell death, as well as cell growth must occur for
  proper development
• Connected to the cell cycle.

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ReviewMitosis vs
Meiosis

• Cell division for reproduction for growth (in
  multi-cellular forms)
• Chromosome number is kept constant from parent
  cells to daughter cells (one cell 2N-gt2 cells
  each 2N)
• All non-gamete cells
• Part of cell cycle

• Cell division for sexual reproduction (gametes)
• Chromosome number is reduced (2n-gt 1N cells)
• Only occurs to make gametes
• Occurs in testes and ovaries

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Cell cycle
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Cytokinesis-rest of the cell divides
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Phases of Mitosis

• Interphase
• Prophase
• Metaphase
• Anaphase
• Telophase
• Animation link(s)
• http//www.lewport.wnyric.org/jwanamaker/animation
  s/mitosis.html
• http//www.sci.sdsu.edu/multimedia/mitosis/mitosis
  _qt1.html
• http//intranet.stgregorys.edu/people/faculty/sway
  /A.C.E.Biology/celldivision-cytokinesis_files/fram
  e.htmslide0020.htm

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Interphase
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Prophase
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Metaphase
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Anaphase
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Telophase
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Then cytokinesis again!!! Entire cell cycle
repeats with the newly formed cells.
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Thoughts on developmentDifferentiation

• What if your entire body was made of only stem
  cells? Muscle cells? Nerve cells?
• Do different types of cells (tissue) perform
  different jobs in a multicellular organism?
• If all of the organisms cells are genetically
  Identical, how do they become different types of
  cells (tissue)?

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Epithelial and Connective
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Nerve and Muscle
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• OKAY???????
• But how does an organism get all of these cell
  (tissue) types?

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DEVELOPMENT MATH IS EVERYWHERE

• DEVELOPMENT Growth Differentiation

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Components of Development

• Growth- The process of a multicellular organism
  increasing its number of cells, becoming larger.
  (i.e. zygote to an adult)
• Differentiation- The process of cells in a
  multicellular organism (initially all alike)
  becoming different from each other generating the
  various tissues (i.e. nerve, muscle, skin and
  bone, etc.) necessary to be a functional adult .

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Historical perspective

• The Homunculus Theory
• A fully formed person, just very tiny, exists in
  the head of a sperm cell. The egg makes no
  contribution except to function as an incubator.
• No differentiation necessary!!!!!!!!!!
• We now know better

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Embryonic differentiationZygotes
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Early embryonic development
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Morula
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Blastula
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Gastrulation
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It is not birth, marriage, or death, but
gastrulation, which is truly the most important
time in your life."             Lewis Wolpert
(1986)
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Embryonic cell (tissue) types

• As embryos develop to the gastrulation stage
  they form three basic types of tissue which
  differentiate into all other tissues
• Endoderm
• Mesoderm
• Ectoderm

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These basic tissues become
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OKAY ??But how do we get to become these
tissues from embryonic stem cells?
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Influences on differentiation(switching genes on
and off)

• Environmental influences both inside the cell and
  outside the cell can cause certain genes to
  switch on or off at appropriate or inappropriate
  times.
• Inside the cell- differential distribution of
  materials during cell division can cause cells to
  develop differently.
• Outside the cell- chemical communication with
  nearby cells may influence development based on
  strength of signal.
• Induction- is a special type of outside
  influence.
• ??????????? (good field for a career)

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Induction!!!
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Homeobox

• Master control genes that other genes relating to
  very complex patters of development.
• Gene sequences found in common among organsms.
• Evolution solves the really complex problems only
  once.

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apoptosis (cell death)
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Apoptosis (cell death) at the appropriate time is
also very vital to development.
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What next?
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Development sometimes messes up!

• Cancer- ones own cells fail to stop reproducing
  when they should.
• Birth defects- environmental factors genetics
  cause misinformation during development.

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Key Development terms

• Zygote
• Blastula
• Gastrulation
• Growth
• Cytokinesis
• Mitosis
• interphase
• prophase
• metaphase
• anaphase
• telophase

• Differentiation
• Senescence
• Cell cycle
• DNA
• Induction
• Cancer
• Metastasis
• Birth defects
• Mutation

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Final thoughts

• Development must occur at the correct times and
  correct places in the embryo.
• Animal development occurs in consistent patterns.
• Plants go through similar development.
• Cell deaths must also occur at appropriate times.
• Development is a zygote to death process.
• Developmental errors often cause spontaneous
  abortions (in humans the rate is approx. 25).
• Environmental factors can greatly influence
  development (especially during very early
  development).
• Development growth differentiation.
• Genes can also switch other genes on or off,
  creating a cascade (ripple effect).
• Homeobox genes are master control genes.
• We still have a lot to learn about development.

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