Download Exam 3 KEY v3 Bio200 Sum12

Biology 200, Summer 2012
Exam 3
VERSION C

Name: _________________________________
Section: _______ TA: _________________
Biology 200
Summer Quarter 2012
Exam #3
DO NOT OPEN EXAM UNTIL DIRECTED TO DO SO
Make sure you have 6 pages, including this one. Print your name and information on ALL pages.

Please use a pen. Pen is much easier to read, even with extensive crossing-out. Pencil-written
exams are acceptable, but it is often difficult to give full credit to penciled answers on regrades.

When asked, provide concise and clearly written answers. We may deduct points if you do not
fully answer the question or if your answer is too vague or too confusing for us to follow. Extra
information, if incorrect, will lose points.

Limit your answers to the space provided. If you need extra space, you can use the bottom of
this first page or extra space on the Take Home page. Indicate “on ___ page” where necessary.
The Big Development Scenario
Questions 1-2 will be about the following development scenario. Not all details are shown.
1.
2.
4.
8.
<Many steps>
(a 3-dimensional
rounded oval made
of many cells)
center
12.
15.
<Many steps>
19.
9.
Example cells
41.
27.
adult
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Biology 200, Summer 2012
Exam 3
Name: _________________________________
Section: _______ TA: _________________
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Biology 200, Summer 2012
Name: _________________________________
Exam 3
Section: _______ TA: _________________
1. [17 points] The Big Development Scenario, Part 1
Use the scenario on page 1 to answer the following questions. These questions will focus on (but are
not limited to) gastrulation and neurulation.
a. [4 pts] Between which steps is gastrulation most likely to be taking place? (Check all that are correct.)
Gastrulation is occurring:
___ Between steps 1 and 2
___ Between steps 2 and 4
_X_ Between steps 4 and 9
___ Between steps 15 and 19
___ Between steps 19 and 27
___ Between steps 27 and 41
b. [4 pts] Evaluate the following statement: “The claw structures in stage 41 are probably grown from ectoderm.”
Do you agree? Why or why not? (Answer in one sentence or less.)
I agree because the neural tube guarantees that this organism has already gastrulated so the outer layer is
ectoderm.
OR
I disagree because the complex structures of the claw probably include some mesoderm and maybe even
extoderm on the inside of the primarily ectodermal structure.
c. [5 pts] On the model below, draw arrows indicating the direction of cell movements that are needed for
development of the spinal column. Put a star where the notochord intersects this cross section. Lastly, draw a
model of the Stage 12 embryo if it were to start expressing notochord signals from all mesodermal cells.
d. [4 pts] If you surgically remove the center cell from a Stage 4 developing embryo, neurulation will not occur.
Removing any other cell does not affect neurulation. What does this tell you about neurulation in the species?
(Answer in 1-2 sentences)
The center cell is already determined to be the notochord, which is needed for spreading the signal to
neurulate.
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Biology 200, Summer 2012
Exam 3
Name: _________________________________
Section: _______ TA: _________________
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Biology 200, Summer 2012
Exam 3
2. [16 points] The Big Development Scenario, Part 2
Name: _________________________________
Section: _______ TA: _________________
Use the scenario on page 1 to answer the following questions. These questions will focus on (but are
not limited to) somites and organogenesis.
a. [4 pts] The protein product of the gene Headless helps to set up the initial body axes in this species. The gene
Clawfree is a homeotic gene. (Check all that are correct.)
_X_ Headless protein maybe necessary to turn on Clawfree gene expression.
___ Clawfree protein may be necessary to turn on Headless gene expression.
_X_ Clawfree is probably expressed at high levels in the lateral structures in stage 19.
___ Headless is probably expressed at high levels in the lateral structures in stage 19.
b. [4 pts] Using what you see in the diagram and what you know about chicken development, give one
similarity and two specific differences between the developmental processes in this species and in chicken. Do
not simply list final structure, and be as specific as possible. (Answer in a few words or a sentence each)
Similarity:
There are many possible answers.
Difference #1:
Chickens use discoidal cleavage to make a flat embryo while this species uses radial cleavage and a
spherical embryo.
Difference #2:
This uses pre-packaged organ-generating cells on the outside of the body plan while those in chicken are
very close to the center.
(There are other possible correct answers)
c. [4 pts] There are 21 example cells shown as circles in stages 9, 12 and 15. Put a star on the two cells most
likely to be part of somites. Stars are on cells near to the neural tube and in the latest possible stage.
15.
12.
9.
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Biology 200, Summer 2012
Name: _________________________________
Exam 3
Section: _______ TA: _________________
d. [4 pts] Occasionally, mutant individuals of this species have two non-functional mutated copies of
the genes needed for claw formation but still have perfectly formed claws. What is going on? There is
a specific clue in the diagram. (Answer in 1 sentence.)
The squiggly lines may represent maternal determinants for claw formation which can be wildtype from the mother even if the embryo is mutant.
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Biology 200, Summer 2012
Name: _________________________________
Exam 3
Section: _______ TA: _________________
3. [18 points] Fill in the blank
For each, write TWO different answers that fit the description given. Be as specific as possible. It is
acceptable to use the same answer for different questions.
The full 3 points will be awarded for a correct pair of answers (+1 for a single correct answer).
Ex) A gene found in sperm cells.
i.
resact
ii. actin polymerase
a) A final fate of a cell from
the mesoderm tissue layer.
i. _____muscle_______ ii. ______bone_______
b) A transcription factor found in
the species Drosophila.
i. _____bicoid_______ ii. _______nanos______
c) A cell with the homeotic gene for
development of neurons.
i. ____sperm________ ii. ______muscle cell___
d). A possible developmental effect of cells
i. ___no neurulation__ ii. ____twins____
that cannot join or hold or intermix with each other.
e) A cleavage pattern that is not radial.
i. ____discoidal_____ ii. _____spherical______
f) Draw the cleavage patterns you used for part e. i. __________________ ii. __________________
4. [10 points] Cellular Developmental Processes
There are five basic cellular developmental processes that a cell can undergo. Using the sentence
prompts below, describe differentiation. For each prompt, answer in one short sentence or less while
being as specific and clear as possible. Be sure to name the species for parts b and c.
a) [3 pts] The basic mechanism is:
Cells receive signals and respond by producing specific role-related molecules and structures that
will enable the cell to perform a specific task.
b) [2 pts] One example in __humans___ (species) is:
Spermatogonium differentiate from their stem cell state through meiosis into differentiated
sperm. (Multiple possible correct answers)
c) [2 pts] An example in ___frogs___(a different species than in part b) is:
Dorsal lip cells give signals that tell embryo cells to move into the middle of the embryo and
become endodermal cells which differentiate to gut lining cells. (Multiple possible correct
answers)
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Biology 200, Summer 2012
Name: _________________________________
Exam 3
Section: _______ TA: _________________
d) [3 pts] “Differentiation is more important than apoptosis.” Do you agree? Why or why not?
Agree, because apoptosis is used for making particular openings or lack of cells but differentiation
is needed for all of those cells to get to that stage anyway. (Multiple possible correct answers)
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Biology 200, Summer 2012
Exam 3
Name: _________________________________
Section: _______ TA: _________________
5. [24 points] Mutation Rays
A bizarre ionosphere storm is producing extremely focused bursts of gamma radiation on earth. These strange
rays instantly affect every one of a specific molecule within each species. World leaders have asked you to help
them predict the effects of several specific effects on key development molecules.
[If multiple choice, check all correct answers. If written, answer specifically in a sentence or less for each.]
a. [4 pts] In sea urchins sperm, actin polymerase is destroyed.
What is the effect, and why? (Answer in 1-2 sentences.)
Sperm will not be able to complete the extension of the acrosomal process, so while bindin might
still reach fertilizin on the oocyte membrane it is likely that fertilization rates will drop
significantly.
b. [4 pts] In frogs, all signal receptors on notochord cells are destroyed.
No answers are correct
___ Mesodermal cells have a hard time becoming notochord.
___ Notochord cells die.
___ Existing notochord cells cannot signal to other cells.
___ Mesodermal cells die.
___ Gastrulation will decrease.
___ Cell intercalation will decrease.
c. [4 pts] In humans, mutation rays make all cell divisions symmetrical. (Answer each in 1 sentence.)
The effect on oogenesis is:
Polar bodies will be larger and oocytes will be smaller, making oogenesis less able to produce
large and very fit oocytes and survival rates will drop.
The effect on spermatogenesis is:
There is no effect on spermatogenesis.
OR
Because spermatogonium cannot regenerate, sperm cannot be produced after all spermatogonium
are used once.
d. [4 pts] In humans, mutation rays destroy the endoplasmic reticulum of all corpus luteum cells.
___ Gastrulation stops in all embryos.
_X_ More oocytes are released each month.
___ Ovaries make too much progestrone.
___ Ovaries make too much estradiol.
___ Neurulation stops in all embryos.
_X_ Development of a single oocyte is unchanged.
e. [4 pts] In sea urchins, sperm and oocytes fuse their membrane less frequently but still do it
sometimes. The mutation ray may have destroyed all of:
___ Bindin
___ Fertilizin
___ Cortical granules
_X_ Resact
_X_ Resact receptor
___ Jelly coat factor
_ok_ Mitochondria
_X_ ½ of all acrosomal digestive enzymes
f. [4 pts] In chickens, a single mutation ray passes straight through a chicken embryo without turning.
The ray goes through an ectodermal cell, then a mesodermal cell, then two endodermal cells, then
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Biology 200, Summer 2012
Name: _________________________________
Exam 3
Section: _______ TA: _________________
another mesodermal cell, and then finally another ectodermal cell. What is the latest major
developmental process that must have occurred in this embryo?
Body folding
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Biology 200, Summer 2012
Exam 3
Name: _________________________________
Section: _______ TA: _________________
6. [15 points] Take Home:
This take home portion should be completed before the exam and turned in at the start of the exam. You can work with
other students, but your words must be your own. Neatness and clarity are important. Course staff (TAs, Ben, or Linda)
will politely refuse to answer questions that directly relate to this take-home portion. You can remove the instructions on
this sheet if you want more room on your version to turn in.
a) [10 points] When you look at the cell of an adult chicken, you are looking at one of the final products of a
lineage of cells that goes back all the way to the original chicken zygote before cleavage. Create a bulleted list
of 10 signals sent or received by this direct cell lineage. You don’t have to include every signal (there are
probably hundreds of possibilities at the least). The signals should be in a reasonable order. (To help clarify: a
direct lineage of your family tree would include your mother, her mother, and her mother’s mother, but would
not include your uncle.) Write or type each signal in a few descriptive and clear words.
Example: “Notochord cell is signaled to re-task to non-signaling role”
1)
2)
3)
[MANY ANSWERS ARE POSSIBLE. WE ARE LOOKING FOR A
LOGICAL ORDER TO YOUR SIGNALS AND INCLUSION OF DIFFERENT
KINDS OF SIGNALS WHERE POSSIBLE.]
4)
5)
6)
7)
8)
9)
10)
b) [5 points] Give three examples of specific signals that this cell did not receive at any time. Make sure to
indicate why you know that signal information was never received by the cell lineage in question. Answer in
1-2 sentences for each.
1)
[MANY ANSWERS ARE POSSIBLE.]
2)
3)
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Biology 200, Summer 2012
Exam 3
Name: _________________________________
Section: _______ TA: _________________
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