Download Model 1: 5 Fundamental Cell Processes underlying

POGIL Cell Biology Activity 8 - Development
Schivell
Model 1: 5 Fundamental Cell Processes underlying
Development (Freeman, 5e, Ch. 22)
1. Cell proliferation ("more-life-making"):
2. Cell differentiation:
3. Cell-cell communication (induction):
4. Cell movements:
5. Programmed Cell Death (Apoptosis): (We won't go into detail much on this
process)
1. For processes 1-3 in the table above, draw a representative sketch of what that process
involves, using what you've learned so far.
2. For process 4, watch these three movies on loop several times: "GFP-Actin Cell movement"
(in which actin filaments appear green), "cell movement" and "Skin tissue motility".
a. Circle the parts of the cell that appear to change shape/structure in order to produce cell
movement. (Circle ALL correct answers)
- nucleus
- plasma membrane
- cytoskeletal proteins
- other organelles
b. Can cells move "together" as a sheet (connected layer of cells)? ______
c. Inside the cell below, actin monomers (a) can polymerize into actin filaments (b). There are
also proteins in the plasma membrane (c). If this cell moves to the right, describe how the actin
and the plasma membrane proteins play a role in facilitating this movement.
a
b
c
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POGIL Cell Biology Activity 8 - Development
Schivell
Model 2: Clay Modeling of Cleavage
3. Holoblastic Cleavage: Take a single ball of clay to represent the fertilized egg (zygote).
Divide the cell in half to represent the first cell division. Divide those cells in half again for the
2nd cell division. Repeat with all cells for a 3rd time.
a. How many cells do you have at this point? ________
b. Is the embryo (all of the cells together) any bigger than the zygote was? ______
c. Are your cells adhering to one another? (If not, you've got octuplets!) What type of
biological macromolecule could help with adhesion?
___________________
d. Examine the stages of the cell cycle to the right.
Which steps must be almost completely skipped during
these cell divisions? How do you know?
M
G1
G2
S
4. The embryo goes through about 10 cell divisions (in which every cell divides) during this
stage of development, and then cell division rates generally slow down.
a. How many cells are there after 10 cell divisions?
~10
~1,000
~1,000,000
b. Why do cell division rates slow? What is needed by cells at this point? (Or think about it
this way – What may have been "used up"?)
5. Meroblastic Cleavage: Clump all of your clay back together to form another zygote. This
time, you will mimic a different kind of cleavage (for animals with large, yolky eggs).
- Carefully form an indentation on one side of the zygote, but don't go all the way
through.
- Repeat but make the next indentation perpendicular to the first, crossing it.
- Repeat two more times, crossing always in the middle.
- It should look something like this:
a. The indentations are called "cleavage furrows".
If cleavage furrows do not go through the zygote
completely, there are many nuclei, however, are they in completely separate cells? ______
b. Generate a new cleavage furrow that is perpendicular to the ones you've made before so
that you create completely independent cells. Check with an instructor to make sure you've
done this correctly.
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POGIL Cell Biology Activity 8 - Development
Schivell
Model 3: Observing Cleavage and Gastrulation Videos
6. Watch the two videos named "Fish Cleavage" and "Sea Urchin Cleavage".
Which developmental process does the "Cleavage" stage rely on? ________________
7. Which animal has holoblastic cleavage? ______________ meroblastic cleavage? ___________
8. Are cell divisions random or synchronized? _________________
9. What is the hollow space inside the sea urchin embryo after cleavage? ___________
10. Watch fish cleavage carefully. The first 13-15 seconds of the video show the cleavage
stage. Make sure to identify the embryo's cells and contrast with the yolk. After the first 13-15
seconds of cleavage, watch what the embryonic cells do with respect to the yolk. Describe it
briefly:
11. Watch the "Human Gastrulation Animation" video.
Which developmental process does the "Gastrulation" stage rely on? ___________________
12. Describe the movement of cells during gastrulation. Include the terms: "primitive streak"
(in the epiblast), "blastocoel", and "hypoblast".
Model 4: Chick Embryo Blastodisk and Gastrulation
Model 4 Diagram is on the separate color page.
13. On the side view at time 1, label "epiblast", "hypoblast", "blastocoel" and "yolk".
14. How did the dark streak down the middle at Time 2 form? Describe in terms of cell
movements (follow the specific cells that are colored).
15. Answer the following based on the changes in the cells that are different colors.
a. The first cells to ingress displace cells of the __________________________.
b. What germ layer do the first cells to ingress become? _____________________
c. What germ layer will the yellow and blue cells be in? _____________________
d. Are cells still dividing in this embryo? __________
16. On the side view at time 5, label "ectoderm", "mesoderm", "endoderm", "hypoblast", and
"yolk".
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POGIL Cell Biology Activity 8 - Development
Schivell
16. From Time 2 onward, cell movements are initiated at the anterior (head) of the embryo
and progress toward the posterior (tail) end over time.
a. Label the 'top view' images with A for anterior and P for posterior.
b. There is a group of cells in this model that signals to the cells around them to move. In
frame 2, those cells are found at the tip of the arrow. For every other frame, indicate
where those cells must be.
c. That small group of cells is referred to as "Hensen's Node". Cells of Hensen's Node make
two signal molecules called "sonic hedgehog" (Shh) and "chordin". What type of protein must
be found in cells surrounding Hensen's Node (if they can respond)?
d. Cells that ingress into the mesodermal layer and then travel anteriorly receive the most Shh
and chordin signaling – these cells become a structure called the notochord. The notochord
cells will signal to overlying ectoderm to become neural. How are the notochord cells different
from other mesodermal cells?
Model 5: Observing and Modeling Neurulation
Watch the "Chick Neurulation" video carefully several times. You are looking down on the
ectoderm. The anterior of the animal is to the right.
17. Describe the general cell movements in neurulation briefly.
18. Flatten your clay into a sheet to represent the cells of the ectoderm. Copy the folding that
you see in the videos. Eventually separate the invaginated part from the overlying part.
a. What structure does this folding eventually produce? _________________________
b. What will that become in the adult organism? ____________________________
19. Draw a cross section of the ectoderm once neurulation is complete. Top should be dorsal,
bottom ventral, sides left and right. (Imagine cutting your clay model in half, left to right).
Label your diagram with skin and neural tissues.
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POGIL Cell Biology Activity 8 - Development
Schivell
Model 6: Neurulation Experiments
This model shows "normal" (WT) neurulation at the top, then several experiments where two
critical signaling molecules (noggin and BMP-4) have been altered (Exp. 1-4) or where parts of
the embryo have been removed (Exp. 5-7). Embryos on the left are pre-neurulation and on the
right are post-neurulation. You are shown the three embryonic germ layers on the left
(top=ectoderm, middle=mesoderm, and bottom=endoderm).
WT
Exp. 1
Add inhibitors of both
noggin and BMP-4
Exp. 2
Add inhibitor of the
signal molecule "BMP-4"
Exp. 3
Add inhibitor of the signal
molecule "noggin"
Exp. 4
Add extra "noggin"
Exp. 5
Exp. 6
Exp. 7
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POGIL Cell Biology Activity 8 - Development
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20. Two signals, noggin and BMP-4, work together during neurulation to determine which
parts of the ectoderm become skin and which parts become neural. Use experiments 1-4 for
the following questions.
a. What is the "default" state of the ectoderm? (Hint: no signal...) __________________________
b. Determine which signal prevents neural tube formation and explain your answer:
21. a. Using the data from experiments 5-7, determine where the signal comes from to initiate
neurulation. (Pick one from each group)
group 1:
group 2:
- mesoderm
- ectoderm
- midline of layer (along the A->P axis)
- endoderm
- sides of layer (left and right)
b. Which signal is most likely released by the cells that you chose in 'a'? How do you know?
c. Which of the following schemes best represents the interaction between the signaling
molecules?
-noggin activates BMP-4
-BMP-4 activates noggin
-noggin inhibits BMP-4
-BMP-4 inhibits noggin
22. Propose a hypothesis for why the endoderm does not respond to the signals in the same
manner as the ectoderm.
23. The cells that make noggin are called the "notochord".
a. In what layer can you find the notochord? _______________
b. Describe the role of the notochord during this phase of development in a few words:
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POGIL Cell Biology Activity 8 - Development
Schivell
Model 7: Body Folding
Model 7 (see color page) shows a time lapse of a chick embryo from top and side views, during
body folding. Starting with a single thin sheet of clay, try to model the changes in structure
over time.
24. a. What layer of tissue are you looking at in the external views?_____________
b. Which end of the embryo shows changes in shape first? Anterior
Posterior
25. Is it only the ectoderm that is folding in this model, or are all layers involved? How do
you know?
26. In the last panel, the endoderm is directly connected to the yolk in only one small area.
Draw an arrow pointing to that area.
27. In the second to last panel a cell at the tip of the arrow in the ectoderm is not directly
touching the yolk. Try to think of two ways the embryo could get nutrients from the yolk to
this cell.
28. In the last panel the digestive tract (endoderm) is an almost complete tube. However, there
are no openings that correspond to the mouth and anus. The embryo uses apoptosis
(programmed cell suicide) to form these. Mark the location(s) in the last diagram where
apoptosis will occur and label them "mouth" and "anus".
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POGIL Cell Biology Activity 8 - Development
Schivell
On Your Own: Note: many of the questions will only be answerable AFTER the chick lab!
1. You are observing embryos in culture (removed from the egg and growing in nutrient-rich
media). Pre-gastrulation, everything has proceeded normally in all cases. Consider each
scenario (a-e) separately. Write a "+" in the box under each developmental process that will
proceed NORMALLY.
Hensen’s
node
forms
Three
embryonic
layers form
Notochord
forms
Neural
tube
forms
+
+
+
+
Example: No mutations or treatments
a. Both copies of the gene encoding the
chordin protein have an early stop codon
at the third amino acid.
b. The embryo has the same mutations as
in Part a. You also transplant the cells of a
Hensen’s node from a normal embryo to
the mutant one
c. You add a chemical that binds and
prevents noggin from functioning,
immediately after the primitive groove
forms.
d. Both copies of the sonic hedgehog
receptor gene are mutated so that the
receptor does not bind its signal molecule.
e. The embryo has the same mutations as
in Part d. You also transplant a normal
Hensen’s node into the mutant embryo.
f. You let the embryo from Part c live in culture for several days.
What cell fate potential best describes most of the cells in the embryo
at the end of this period? (Circle ONE)
Determined
Pluripotent
Differentiated
Holoblastic
g. You have another normal (not mutant) embryo. When it reaches this stage,
you add the chemical from Part c. In the picture, circle the region of the embryo
that should continue to develop NORMALLY.
h. In the embryo in "g", which of the following will NEVER be
found in the chick? (Circle ALL that apply)
Somites
Anus
Tail
Eye
Mouth
Posterior Intestinal Portal
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Hensen's
Node
POGIL Cell Biology Activity 8 - Development
2. The figure to the right shows a cross-section
of an embryo at the primitive streak/groove stage.
Schivell
C (top layer)
B (space)
a. Name each structure:
A: _________________
YOLK
B: _________________
A (bottom layer)
C: _________________
1 (tube)
b. To the right is an older chick embryo (as it looks on
top of the yolk). Write the name of each of the labeled
structures. Then circle the letter from the figure of the
primitive groove that corresponds to the structure that
will produce cells for this part of the older embryo.
1. name: _______________________ from: A
B
C
2. name: _______________________ from: A
B
C
3. name: _______________________ from: A
B
C
c. The cells in the structures labeled with “3” will eventually
become muscle and bone. What level of cell fate restriction
have these cells reached (at the stage in the drawing)?
____________________________
3
(pairs of
“brick-like”)
structures
2
d. In some of the embryos studied in lab, cells were moving through the structures labeled
with “2”.
i. What is the name of these cells? ___________________________
ii. What level of cell fate restriction have these cells reached? _______________________
d. When cells in the structure labeled “2” go through the cell cycle and divide, which of the
following proteins or protein complexes will be present in the cells? (Circle ALL that apply)
- ATP synthase
- kinetochores
- DNA polymerase I
- synaptonemal complex
e. Which structures in the embryo contain the noggin gene? (Circle all that apply) 1
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2
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POGIL Cell Biology Activity 8 - Development
Schivell
3. The cells in the zygote/early embryo do not have time to make all of the ATP they need,
transcribe lots of mRNA or to translate all of their own proteins, yet they are still alive and
functioning. Explain this using what you learned about oogenesis.
4. The questions below refer to the mutant
chick embryo to the right.
a. How many of each of the following structures
either have been or are currently associated with
this embryo?
i. hearts: ________
iii. Hensen’s nodes: ________
ii. yolks: ________
iv. notochords: ________
b. In the diagram, circle a region in which you can find
differentiated cells and explain how you know that they are differentiated below:
c. Which of the following reasons is the BEST explanation for how this embryo arose? (Circle
ONE)
- The hen that laid this egg ovulated two oocytes.
- Notochord cells made too much of their signaling molecule
- Cell adhesion between cells of Hensen’s node was weak
- Hensen’s node did not produce chordin protein.
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POGIL Cell Biology Activity 8 - Development
Schivell
Model 4: Chick Embryo Blastodisk and Gastrulation
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POGIL Cell Biology Activity 8 - Development
Schivell
Model 7: Body Folding Images
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