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Lactose operon concept is v. useful consept. I faced many ques in UW... Can anyone explain it in easy words?? plz dnt use kaplan's language.. i had already read thrice bt couldnt undrstand...
 

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Lactose operon concept is v. useful consept. I faced many ques in UW... Can anyone explain it in easy words?? plz dnt use kaplan's language.. i had already read thrice bt couldnt undrstand...
hmm in this case i would suggest u watch this video. It surely helped me to grasp the concept

 

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Is this topic high yield for the step? I know it's referenced heavily in UW, but I remember hearing somewhere its' not tested that much on the actual step...
 

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Check out this diagram (from Wikipedia):



The summary is that the lac operon is highly active only where there's HIGH lactose and LOW glucose. When glucose is abundant, it's inhibited by the action of a lac repressor protein covering the expression sites. When lactose is abundant and glucose is low, lac repressor protein is detached, and the expression sites are exposed, on which catabolite activator protein (CAP) acts. This leads to metabolism of lactose yielding B-galactosidase & permease. This provides energy for the bacteria.
 

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The lac operon is pretty HY. They explained it in detail in the Kaplan videos, and UW has a lot of questions on it. But as far as it gets, all you need to know about it is the summary I mentioned above. Remember that biochemistry as a whole is LY. Only 5% of the exam is bio.
 

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lac operon is very high yield for the exam

By the way this lac operon thing is very very high yield for the USMLE Step 1 you have to know it from A to Z
 

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I think it's high yield

Dr. Brian Jenkins from DIT mentions it in his course, although i'm not sure if it's in FA. I read it from Lippincott's Biochemistry the first time and didn't get it. The videos posted here are awesome and thanks for those. If you want to read it from a book, I think the best explanation I've read so far was in HY cell and molecular biology (go figure). :p
 

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Is it time to resurrect this topic? Yes! I just came across 3-4 questions like this in UW and I was disappointed in my performance. I ran to my First Aid (my first stop for high yield info) and I was left empty handed. Next, I carefully combed through the answer explanations in UW to get a better understanding. That's when the wheels started turning for me. Finally, I searched online and found this post at usmle-forums*com! I really like Haisook's summary. The combination of resources helped me to learn the topic well (enough) for the questions I missed. I'm hopeful that I will not miss these questions on the real exam.

Thanks again for posting this (Back in 2010! I absolutely love the internet!)

~Sincerely,

Russell
 
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