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Ok, I'm not a bad guy. I preach that the MCAT is by far the most important aspect of your application, but I never actually post on this side of the forum. I've got some time to kill before med school starts in the fall, and I just finished a paper. I decided to post the abstract and ask a few questions to show you guys what skills you need for the "new" MCAT Bio before I got out tonight. I hope this helps. Passage below and some questions after that.
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Inflammation is linked clinically and epidemiologi- cally to cancer, and NF-kB appears to play a causa- tive role, but the mechanisms are poorly understood. We show that transient activation of Src oncoprotein can mediate an epigenetic switch from immortalized breast cells to a stably transformed line that forms self-renewing mammospheres that contain cancer stem cells. Src activation triggers an inflammatory response mediated by NF-kB that directly activates Lin28 transcription and rapidly reduces let-7 micro- RNA levels. Let-7 directly inhibits IL6 expression, re- sulting in higher levels of IL6 than achieved by NF-kB activation. IL6-mediated activation of the STAT3 transcription factor is necessary for transformation, and IL6 activates NF-kB, thereby completing a posi- tive feedback loop. This regulatory circuit operates in other cancer cells lines, and its transcriptional signature is found in human cancer tissues. Thus, inflammation activates a positive feedback loop that maintains the epigenetic transformed state for many generations in the absence of the inducing signal.
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1) First, whenever you see a passage like this ALWAYS draw out the pathway. So do just that. Use --> for stimulates and ---l for inhibits.
2) Based on the passage how can NfkB be classified.
a) a restriction factor
b) a transcription factor
c) a DNA methyl transferase
d) a cytokine
3) If the scientists in the passage had over expressed in let 7 in the cell lines, what effect would this have on cellular transformation.
a) It would increase levels of cellular transformation.
b) Decrease levels of cellular transformation.
c) Have no effect since IL6 positively feedbacks on NFKB leading to cellular transformation regardless of let 7.
d) WTF? Who cares, these questions are nothing like the Kaplan tests...
4) Overexpression of SRC in cell lines of Stat 3 -/- mice would have which of the following effects?
a) Epigenetic switch leading to increased cellular transformation.
b) Decreased expression of Lin28.
c) Lower levels of inflammation due to down regulation of IL6.
d) Increased levels in Lin28 and IL6, yet no epigenetic switch to cellular transformation.
5) Which of the following statements is false?
I) The mechanistic regulation of cellular transformation described is dependent on changes in DNA sequences of target genes.
II) IL6 positively feedbacks on NFKB.
III) Overexpression of Lin28 in breast cells leads to increased levels of cellular transformation.
a) I
b) II
c) III
d) I and III
e) II and III
f) I and II
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Inflammation is linked clinically and epidemiologi- cally to cancer, and NF-kB appears to play a causa- tive role, but the mechanisms are poorly understood. We show that transient activation of Src oncoprotein can mediate an epigenetic switch from immortalized breast cells to a stably transformed line that forms self-renewing mammospheres that contain cancer stem cells. Src activation triggers an inflammatory response mediated by NF-kB that directly activates Lin28 transcription and rapidly reduces let-7 micro- RNA levels. Let-7 directly inhibits IL6 expression, re- sulting in higher levels of IL6 than achieved by NF-kB activation. IL6-mediated activation of the STAT3 transcription factor is necessary for transformation, and IL6 activates NF-kB, thereby completing a posi- tive feedback loop. This regulatory circuit operates in other cancer cells lines, and its transcriptional signature is found in human cancer tissues. Thus, inflammation activates a positive feedback loop that maintains the epigenetic transformed state for many generations in the absence of the inducing signal.
-------------------
1) First, whenever you see a passage like this ALWAYS draw out the pathway. So do just that. Use --> for stimulates and ---l for inhibits.
2) Based on the passage how can NfkB be classified.
a) a restriction factor
b) a transcription factor
c) a DNA methyl transferase
d) a cytokine
3) If the scientists in the passage had over expressed in let 7 in the cell lines, what effect would this have on cellular transformation.
a) It would increase levels of cellular transformation.
b) Decrease levels of cellular transformation.
c) Have no effect since IL6 positively feedbacks on NFKB leading to cellular transformation regardless of let 7.
d) WTF? Who cares, these questions are nothing like the Kaplan tests...
4) Overexpression of SRC in cell lines of Stat 3 -/- mice would have which of the following effects?
a) Epigenetic switch leading to increased cellular transformation.
b) Decreased expression of Lin28.
c) Lower levels of inflammation due to down regulation of IL6.
d) Increased levels in Lin28 and IL6, yet no epigenetic switch to cellular transformation.
5) Which of the following statements is false?
I) The mechanistic regulation of cellular transformation described is dependent on changes in DNA sequences of target genes.
II) IL6 positively feedbacks on NFKB.
III) Overexpression of Lin28 in breast cells leads to increased levels of cellular transformation.
a) I
b) II
c) III
d) I and III
e) II and III
f) I and II