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Short Paper Number       Name

Instructions:This examination is aimed at measuring your creativity, your abilities in logical thinking andwriting (including drawing schematics), and your basic knowledge in biology. The setting of thequestion is basically imaginary. You are free to choose experimental settings unless they aredescribed, but please describe your settings clearly in the answer sheet.
When we evaluate the answers, we will take your research background and future researchinterests into consideration.
Even if you cannot answer a given question (or a part of a question), you may be able to answer
subsequent questions (or subsequent parts of a question).

Read the following story and answer Questions 1 to 5.
* Effective use of schematics and/or tables is highly recommended.
* When multiple answers are requested, answers from different angles are preferable.
* Please write and draw your answers within the assigned spaces in the answer sheet by pencil.
*You may use the provided scratch paper for your own notes but only material in the assigned
spaces will be evaluated.

1

Short Paper Number       Name

Marine multicellular organism A is colorless at birth but its exterior turns black during
development and remains so through adulthood.
Dr. Mishima became interested in the mechanism of body color change of organism A.
She performed three experiments described below. All individuals used in theexperiments were genetically identical.
Experimental result 1 Organism A individuals were split into two groups. One group
was kept under continuous light and the other group was kept in complete darkness afterhatching. All individuals kept in the light turned black but all individuals kept in thedark remained colorless.
Experimental result 2 When only a portion of the body, rather than the whole body,was illuminated for a long time, the whole body of organism A individuals turned black.
Experimental result 3 The body fluid was collected from a black individual fromExperiment 1. This body fluid was injected into a large number of newly hatchedindividuals. All injected individuals became black in both the light and the dark
conditions. Then, this experiment was repeated for the body fluids of all black
individuals from Experiment 1. The results were same as above.
Q1 Based on the results, propose a simple mechanism of the body color change fromcolorless to black in organism A. Please use schematics (diagrams) to indicate how yourmechanism explains the results of experiments 1, 2, and 3 above.

To further examine the mechanism of body color change in organism A, Dr. Mishima
mutagenized organism A and obtained two mutant lines (mutants W and X) in which
the body remains colorless even when illuminated.
The body fluid of wild type (unmutated) organism A (either illuminated or kept in thedark) was injected into mutants W and X, respectively. The injected individuals wereilluminated and then their body color was observed. The results are shown in Table 1.

2

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Table 1
Body color of mutants after illumination
Mutant W
Mutant X
Body fluid of theilluminated wild type
Body fluid of the wild typekept in the dark

blackcolorlesscolorlesscolorless

Q2 Please explain which parts of the mechanism you described above (your answer toQ1) are impaired by mutation W and mutation X. Please use schematics to explain theeffects of the mutations. If you can not explain the effects of mutations based on themechanism (your answer to Q1), please propose a modification of your model so that it
can account for the findings in Table 1 and then describe your answer.
Microscopy of the epidermis (outer skin cells) of the wild type revealed a mixture ofround and rectangular cells. In black individuals, only rectangular cells are pigmented(Fig. 1A).
In order to examine the functions of the round and rectangular cells, individual cells ofcolorless individuals of the wild type were separated. Then, the separated round andrectangular cells were incubated, respectively, in the body liquid of the colorless wildtype in the dark.
When the respective cell cultures were illuminated for 24 hours, the cells stayedcolorless (Fig. 1B). However, when the illuminated round and rectangular cell cultures
were mixed, the rectangular cells turned black (Fig. 1C).

3

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Figure 1

Q3-1 Based on the results shown in Fig. 1, explain the functions of the round andrectangular cells, respectively, in the body color change of organism A. Please use
schematics in your explanation.

Dr. Mishima further screened body color mutants of organism A and found two mutants(mutants Y and Z), in which the epidermis turns black without illumination.
The mutants Y and Z were grown in the dark. Their body fluid was collected andinjected into colorless wild-type individuals. The injected individuals were kept in thedark and their eventual colors are shown in Table 2.
Table 2
Mutant from which body fluid was collected*
Mutant Y
Mutant Z

Body color of injected wild type**
Black
Colorless*Mutant individuals were kept in the dark prior to body fluid collection.
**Wild-type individuals were kept in the dark prior to, and following, injection.

4Short Paper Number       Name

Q3-2 Based on the results shown in Table 2, explain how the mutations Y and Z
impaired the mechanism of body color change you proposed above. In your explanation,please focus on the functions of the round and rectangular cells described in youranswer to Q3-1.
Q3-3 Body fluid, round cells and rectangular cells were collected from wild-type
individuals as well as from mutant Y and Z individuals. Using this material, propose anexperiment(s) to test your explanation in Q3-2 for the effects of the mutations. Pleasebriefly indicate how the results of your proposed experiment(s) will support/refute yourhypothesis. [Note that you do not have to use all of the collected material in yourexperiments.]

Organisms B and C are marine species closely related to organism A. Dr. Mishima
collected individuals of these species and conducted light exposure experiments to testfor differences in pigmentation timing. 100 individuals of each species were exposed tolight upon hatching and the time till onset of pigmentation was measured. The result isshown in Fig. 2.
Figure 25

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Q4-1 Please briefly describe in words the main findings of this experiment (similaritiesand differences among species) shown in Fig. 2.
Q4-2 Please provide hypotheses for how the pigmentation timing patterns of organisms
A, B, and C are related to the survival of each species in its respective naturalenvironment. You can assume that the timing patterns in the laboratory (shown in Fig.
2) are identical to timing patterns in the natural environments of the organisms.

Q5 You are asked to conduct research related to the body color changes of organisms A,B, and/or C. You can focus on any topic or finding described above. Please construct aproposal that includes the following parts: “title of research”, “research aims”, “outlineof experiments/analyses” and “expected results and conclusions”. Note that theproposed research may focus on any of the organisms, or combination of organisms,described above (A, B, and/or C).

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Answer sheet NumberName

Note that the exam questions are only briefly summarized in the answer sheet. Please be sure to read theexam for the full information and questions.
Q1 Simple mechanism of the body color change from colorless to black in organism A. Please use
schematics (diagrams) to indicate how your mechanism explains the results of experiments 1, 2, and 3 in thetext.

Answer sheet NumberName

Q2-1 Please explain which parts of the mechanism you described above (your answer to Q1) are impairedby mutation W and mutation X. Please use schematics to explain the effects of the mutations. If you can notexplain the effects of mutations based on the mechanism (your answer to Q1), please propose amodification of your model so that it can account for the findings in Table 1 and then describe your answer.

Answer sheet NumberName

Q3-1 Based on the results shown in Fig. 1, explain the functions of the round and rectangular cells,
respectively, in the body color change of organism A. Please use schematics in your explanation.

Q3-2 Based on the results shown in Table 2, explain how the mutations Y and Z impaired the mechanism ofbody color change you proposed above. In your explanation, please focus on the functions of the round andrectangular cells described in your answer to Q3-1.

Answer sheet NumberName

Q3-3 An experiment(s) to test your explanation in Q3-2. Please briefly indicate how the results of yourproposed experiment(s) will support/refute your hypothesis.

Answer sheet NumberName

Q4-1 Briefly describe in words the main findings of this experiment (similarities and differences amongspecies) shown in Fig. 2.

Q4-2 Provide hypotheses for how the pigmentation timing patterns of organisms A, B, and C are related tothe survival of each species in its respective natural environment. You can assume that the timing patterns
in the laboratory (shown in Fig. 2) are identical to timing patterns in the natural environments of theorganisms.

Answer sheet Number
Q5 Research Proposal
Title:

Specific aims:

Outline of experiments/analyses:

Expected results and conclusions:Name