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
protein NH3+-GFP-GR-COO-
where GFP is the green fluorescent protein and GR is the
glucocorticoid hormone receptor |
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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. |
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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 MMTV/v-ras/BPV genes.
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 Discussion.
- Figure 4, Figure 6 and Figure 5 taken together
- Figure 7
- Figure 8
Submitting your assignment
Note on grading: In assigning a grade, some consideration
may be given to how the answer communicates your ideas. Keep in
mind the following: