Transcript Cell differentiation

Division of Labor
How a multicellular organism gets from single cell to
millions of highly specialized cells
Emergent Properties
 Each table should have pile of images and
several statements or quotes.
 The term “emergent properties” basically
means that the whole is greater than the sum of
the parts. Looking at the images and
statements/quotes, work together to explain
what “emergent properties” means in terms
of the molecules, cells, tissues, etc. in our
body.
Emergent Properties
 Multicellular organisms show emergent properties. For
example: cells form tissues, tissues form organs, organs
form organ systems and organ systems form multicellular
organisms. The idea is that the whole is greater than the
composition of its parts. The cells by themselves aren’t
much use. It is the many cells working as a unit that
allow tissues, organs, and organisms to perform their
function.
 Emergence is the way complex systems and patterns arise
out of a collection of relatively simple interactions.
 Examples?
Meiosis or Mitosis?
Meiosis or Mitosis?
 Things to think about…
 Is this a process of making gametes (sex cells)? Or do
some of these cells become something other than
gametes?
 Do all of these cells contain the same genetic
information?
Meiosis or Mitosis?
 How do we go from gametes to a “full-fledged”
organism?
 Fertilization (egg + sperm meet) = zygote.
 Many rounds of cell division (we do need more than one
cell to perform all our many functions, after all!). This cell
division is called MITOSIS.
 Cells become specialized.
Egg + Sperm…
 Let’s watch what happens…
Early stages of embryogenesis
 Zygote: single fertilized egg
to ball of less than 16 cells.
 Morula: dense ball of (at
least) 16 cells.
 Blastula: hollow ball of cells.
 Blastocyst
 Gastrula: hollow ball of cells
with different “cavities” inside.
 Neurula: “ with neural tube.
 ….
Early stages of embryogenesis
 Blastocyst (follows
blastula stage in
mammals): Hollow ball of
cells with “inner cell
mass.”
 Trophoblast: outer layer
cells of blastocyst that
become the placenta in
mammals.
 Inner cell mass core of
cells inside trophoblast;
becomes the fetus.
What’s next?
 What needs to
happen to get
from this…
 To this?
Take a moment…
 Think of any type of organism.
Organisms are defined in part by
their shape
 Morphology: the form and structure of an
organism.
 _____________: The process of forming the shape
and structure of an organism and its parts.
Organisms are defined in part by
their shape
 Morphology: the form and structure of an
organism.
 Morphogenesis: The process of forming the
shape and structure of an organism and its parts.
Morphogenesis in the context of
embryology
Egg to fetus
What determines morphology?
About 7 weeks postconception
About 12 weeks postconception
What determines morphology?
 Morphogenesis is controlled by a process called
cell differentiation.
What determines morphology?
 Morphogenesis is controlled by a process called
cell differentiation.
Think - Pair - Share
 What do you think “cell differentiation” means?
What determines morphology?
 Morphogenesis is controlled by a process called
cell differentiation.
 Cell differentiation: process of a cell taking on its
mature form and role for an organism.
 A cell becomes differentiated by producing specific
proteins from the DNA template that allow it to
develop into its mature form.
 Differentiation results in cells taking on their mature form
and function, which are all related to that cell’s structure.
Cell
Differentiation
Morphogenesis
Cell
Morphology
(Shape)
Cell Signaling
 In order to differentiate, cells must somehow “talk”
with each other to decide which cells become
what.
Apoptosis: Example of Cell
Signaling
 Apoptosis: Programmed cell death
 Controlled by cell signals
 Extracellularly: hormones
 Intracellularly: due to cell stress, such as binding
of nuclear receptors by viruses.
 Important for morphology of organism… can
you think why this might be?
Apoptosis: Example of Cell
Signaling
 Apoptosis: Programmed cell death
 Controlled by cell signals
 Extracellularly: hormones
 Intracellularly: due to cell stress, such as binding
of nuclear receptors by viruses.
Think - Pair Share
 Important for morphology of organism… can
you think why this might be?
Apoptosis
About 7 weeks postconception
About 12 weeks postconception
Induction
 Induction: the initiation or cause of a
change/process
 Happens via cell communication (cell signaling)
 Results in different genes being turned on or off.
Regulatory Cascades
SIGNAL
Gene 1
Gene 1 activates
expression of Gene 2
Gene 2
Gene 2 activates
expression of Gene 3
Gene 3
And so
on…
Cell Differentiation
 Cells in a developing embryo begin to differentiate
when they are induced to do so by various signals.
Genes and function
 Chromosome
 Gene
 Intron
 Exon
 Protein
 Gene regulation
 Differentiation
 Morphogenesis
Example of induction and
differentiation at work!
 The pressing question… meiosis or mitosis?
Meiosis or Mitosis?
 How do we go from gametes to a “full-fledged”
organism?
 Fertilization (egg + sperm meet) = zygote.
 Many rounds of cell division (we do need more than one
cell to perform all our many functions, after all!). This cell
division is called MITOSIS.
 Cells become specialized.
Meiosis or Mitosis?
 How do we go from gametes to a “full-fledged”
organism?
 Fertilization (egg + sperm meet) = zygote.
 Many rounds of cell division (we do need more than one
cell to perform all our many functions, after all!). This cell
division is called MITOSIS.
 Cells become specialized.
Meiosis or Mitosis?
 How do we go from gametes to a “full-fledged”
organism?
 Fertilization (egg + sperm meet) = zygote.
 Many rounds of cell division (we do need more than one
cell to perform all our many functions, after all!). This cell
division is called MITOSIS.
 Cells become specialized.
• Note: Up through the
BLASTULA stage, cells
are UNDIFFERENTIATED
Write this down!!!
How do “sex cells” become “sex
cells?”
 A germ cell is a cell that gives rise to sex cells. The very first
germ cells are called “primordial germ cells” and are initially
located outside of the sex organs. (Primordial means “original”
or “the first”).
Migrate to sex
organs. Divide while
migrating.
Primordial
germ cells
(diploid)
Germ cells
(diploid)
Gametes
(haploid)
How do “sex cells” become “sex
cells?”
 Primordial germ cells originate near the cells in the developing
embryo that eventually become the gut.
Endoderm (gut)
How do “sex cells” become “sex
cells?”
 What determines which cells
become primordial germ cells in the
early embryo?
1.
2.
Asymmetrical cell division (in animals
other than mammals and birds)
Induction by neighboring cells (in
mammals and birds)
How do “sex cells” become “sex
cells?”
1. Asymmetric cell division
= “sex cell
molecule”
How do “sex cells” become “sex
cells?”
1. Induction by neighboring cells
How do “sex cells” become “sex
cells?”
1. Induction by neighboring cells
Hey, you guys.
Become a sex cell!
An Example of Genetic Control of
Differentiation
 Your table has been given a description of a cell type.
 Next to the cell type, write the function of that cell and
any special structures and shapes (morphology) or
organelles that cell might need in order to function the
way it does.
 How does this morphology relate to the function of the
cell?
 What genes need to be turned on in this cell?
Type of cell
Function
Morphology
Genes
Velcro cell
Sticks to objects;
holds objects
together and
prevents them from
separating
Cell membrane
contains
interlocking
components
Genes turned on for
making interlocking cell
membrane proteins;
proteins that provide
strength and flexibility
to interlocking cell
membrane
 Your table has been given a description of a cell type.
 Next to the cell type, write the function of that cell and
any special structures and shapes (morphology) or
organelles that cell might need in order to function the
way it does.
 How does this morphology relate to the function of the
cell?
 What genes need to be turned on in this cell?