October 9, 2018
This assignment is worth 5% of the course grade.
Due in class, Tuesday Oct. 23.
To create a model system for studying chromatin folding and
unfolding, a cell line was established for which two constructs
were stably inserted at separate chromosomal loci:
|an array of about 200 tandem
copies of a 9 kb sequence. The 9kb sequence consists of the
mouse mammary tumor virus (MMTV) promoter, driving the viral
genes v-ras and BPV.
|a gene encoding a chimeric
where GFP is the green fluorescent protein and GR is the
glucocorticoid hormone receptor
Figure 2 shows that
a) In cells without hormone treatment, GFP-GR protein
fluorescence is only detected in the cytoplasm.
Hybridization of the same slide with a v-ras/BPV probe
(RNA-FISH) showed no transcript.
b) In cells treated with the corticosteroid hormone
dexamethasone, GFP-GR is only found in the nucleus, while
the v-ras/BPV transcript (circled) is seen as a bright
signal against a background of fluorescence. The same cell,
visualized at the appropriate wavelength for RNA
flourescence, shows that the v-ras/BPV transcript is only
present at a single locus.
Note: Some of these figures do not
reproduce well in grayscale, so you need to either print in
color or view them on a screen.
1) (1 point) State a plausible hypothesis that links the
observations about the glucocorticoid receptor and the
2) (3 points) For each of the following figures, write 1 or 2
declarative sentences that state the key observation from the
figure(s) ie. what is the "take home lesson"?
3) (1 points) Write a concise and precise discussion putting all
the observations from parts 1 and 2 together. In other words, what
were these experiments designed to show us about the relationship
between chromatin structure and gene expression? Some analysis is
requried here; simply restating what you said in 1 and 2 is not
sufficient. Think of 1 and 2 as the Results, and part 3 as the
- Make sure your assignment report includes your name, student
number and UM email address.
- Feel free to include graphs, figures, tables, anything that
gets your point across.
- Save your assignment report as a PDF file, and upload it to
the PLNT3140 UMLearn dropbox site in the Assignment 2 folder.
Files in word processing formats (.doc, .docx, .rtf, .odt) are NOT
Note on grading: In assigning a grade, some consideration
may be given to how the answer communicates your ideas. Keep in
mind the following:
Note on academic integrity: The results shown in this
assignment may be derived from the research literature. It will be
considered a breach of academic integrity to search for the paper on
the Internet and simply copy the author's conclusions from the
- Use precise and appropriate biological terms.
- Organization the ideas in your answer, so that a clear chain
of logic is apparent. Formatting tools such as s subheadings or
bullet points help to show the reader the structure of your
- Ambiguity: Try to read your answers from the viewpoint of your
reader. Are there several possible ways to interpret what you
- Feel free to use figures or tables in cases where they will be
useful get across your ideas.
- Your first step should NOT be to go into the literature and
find papers on the topic. I want to see your
interpretation of the data, not someone else's. All the
information you need is given in this assignment.
- Be careful not to go beyond what the data is telling you. In
other words, state only those conclusions that are actually
supported by the data given here. It's perfectly legitimate to
include sentences like "These results are consistent with what
we know about glucocorticoid receptors...." but make it clear
what you can actually conclude from this data, versus other
points you wish to bring in.
Notes: If you have questions, it may help to
send me a
messge at email@example.com.