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  1. #1
    YuQX is offline Junior Member 510 points
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    A Qbank Question

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    Here is a Qbank question. I don't understand what they are talking about.
    Anybody can give me a help?

    A woman who is heterozygous for glucose-6-phosphate dehydrogenase (G6PD), a polymorphic enzyme transcribed from the X chromosome, develops chronic myeloid leukemia. Restriction fragment length polymorphism (RFLP) studies on the tumor cells for G6PD reveal that only a single form of the enzyme is transcribed. This finding supports which of the following features of neoplasia?


    A Genetic mutation
    B Monoclonality
    C Mosaicism
    D Oncogene activation
    E Point mutation.

  2. #2
    jameslynton's Avatar
    jameslynton is offline Super Moderator 48 points
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    Quote Originally Posted by YuQX
    Here is a Qbank question. I don't understand what they are talking about.
    Anybody can give me a help?

    A woman who is heterozygous for glucose-6-phosphate dehydrogenase (G6PD), a polymorphic enzyme transcribed from the X chromosome, develops chronic myeloid leukemia. Restriction fragment length polymorphism (RFLP) studies on the tumor cells for G6PD reveal that only a single form of the enzyme is transcribed. This finding supports which of the following features of neoplasia?


    A Genetic mutation
    B Monoclonality
    C Mosaicism
    D Oncogene activation
    E Point mutation.
    Hi YuQX,
    Here is my take - B - reason and logic she is heterozygous for glucose-6-phosphate dehydrogenase - studies on the tumor cells for G6PD reveal that only a single form of the enzyme is transcribed - this a polymorphic enzyme therefore the neoplasm has only one set of DNA since being heterozygous she would produce two sets - thus monoclonality is the cause. Distractors are "chronic myeloid leukemia also known as CML", X chromosome not relivant to the disease, and glucose-6-phosphate dehydrogenase - while a not relivant to the disease is a clue to the neoplasm nature. CML often is associated with the philadelphia chromsome. However, several books list it as monoclonal neoplasm. (see First Aid and other sources and the m-protein is often seen as a monoclonal in the neoplasm also). hope this helps.
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  3. #3
    jameslynton's Avatar
    jameslynton is offline Super Moderator 48 points
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    Quote Originally Posted by YuQX
    Here is a Qbank question. I don't understand what they are talking about.
    Anybody can give me a help?

    A woman who is heterozygous for glucose-6-phosphate dehydrogenase (G6PD), a polymorphic enzyme transcribed from the X chromosome, develops chronic myeloid leukemia. Restriction fragment length polymorphism (RFLP) studies on the tumor cells for G6PD reveal that only a single form of the enzyme is transcribed. This finding supports which of the following features of neoplasia?


    A Genetic mutation
    B Monoclonality
    C Mosaicism
    D Oncogene activation
    E Point mutation.
    By reverse logic A & E will most likely not produce G6PD at all - mutations 99% percent of the time don't produce a viable protein. C - crossing over would produce a thrid type of G6PD and D - would not produce one copy as that is a process on a defective gene. Hope this helps.
    Last edited by jameslynton; 06-11-2006 at 08:48 PM.
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  4. #4
    YuQX is offline Junior Member 510 points
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    Hi, jameslynton:
    You are totally right.
    I am not familiar with this kind of topic and CML mixed with G6PD makes me so puzzled. Can you suggest me which material I should study to improve it? Biochemistry?

  5. #5
    jameslynton's Avatar
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    Quote Originally Posted by YuQX
    Hi, jameslynton:
    You are totally right.
    I am not familiar with this kind of topic and CML mixed with G6PD makes me so puzzled. Can you suggest me which material I should study to improve it? Biochemistry?
    This is one of those Dr Goljan integration questions - pathlogy of a most common cancer CML, genetics if you took in college or got it in medical school knowing hetro vs homo traits in genetics - cancer cells often are halpoid - only having 1/2 the chromsomes also called monoclonial - cell physiology DNA to t-RNA to protein - the biochem is a distractor actually other than being a clue. G6PD is a most common enzyme but is has mutlible forms because it can be made to morph or change shape - but it is the clue that says it is how the cancer operates - basic patho-Biochemistry. The trick is you have to put them together.

    So you have to know how proteins are decoded in inhertance. It is best to deconstruct the question like I did on the reverse side of the second post.
    Memory will not do it , review will not do it, compounding basic concepts and vocabulary will help you solve it. I hope this helps. The problem is designed to confuse you. From what I hear on SDN - more questions on the current test are like this. Concept based - takes several steps to solve the clues.
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  6. #6
    YuQX is offline Junior Member 510 points
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    No problem for me to understand these basic concepts, it's problem with the integration and distractors. And Bioengineering is my weakness.
    Hope I will get better when I done more question practice.
    Thank you so much for your kind help!

  7. #7
    jameslynton's Avatar
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    Three resources that may help

    Thanks, you may want to try different q-banks that are more in with the actual tests - Goljan's Pathology Rapid Review has a CD with the book and the book has great questions in it - USMLE Step 1 made ridculously simple has a CD and the Lange paper q-bank I find really good also. While they don't have the spelled out answers that the Kaplan does - they do have more integrative type questions to help get you there.
    I find the Lippincott's Illustrated Reviews 3rd edition of Biochemistry. It has great pictures - it is just a list of facts at first - then about page 150 it starts being more biochem - pathology in it. Give it a try as your Step 1 resource. Don't be afraid to chuck a book if it is not working for you in your studies.
    I think the Goljan lectures pull alot together for me, you really want to think about the questions like a medical detective. Condition X clue, what do the clues mean??? Can you figure out in 35 seconds what is being asked. Then on review - Am I missing the questions because I don't have knowledge of the area etc. For me I suck with anatomy and syndromes.
    Last edited by jameslynton; 06-12-2006 at 07:20 AM.
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  8. #8
    YuQX is offline Junior Member 510 points
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    There are a few things wrong when I did this question. First, I thought G6PD standing for G6PD deficency. In my mind, it is one person with G6PD deficency got CML (What a nerve!). Actually G6PD here is only one tool to distinguish the source of cells. Secondly, I have to say my molecular Biology knowledge is so old. When I see monoclonality, I only can think about monoclonal antibody,which I learned in medical school long long time ago. I am too new to use clone techique to differentiate cells. I know for most people here this question is very easy, but for me, it's a big time.
    I did Goljan's questions in his rapid review book. I am fine with that. Because his question bank CD has too much overlapping with the questions on the book. I lose the interest to carry on and left there.
    Thank you for your suggestion about other question banks, but I don't think I still have time to do them because only one and half month left. I try to finish Qbank this moment (half finished only). I found Qbank got very challenging questions for me. I like Lippincott's Biochemistry as well. It updates my molecular biology lots, and pictures are very good, but maybe a little bit too much somewhere. So, I have to skip some.
    I like the way you're thinking, very logic. I guess you are a very good learner (Sorry I guess everything cos we did too much guessing in USMLE questions)
    Good luck for your study and future career!
    YuQX
    Last edited by YuQX; 06-12-2006 at 11:46 AM.

  9. #9
    jameslynton's Avatar
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    Hey good luck to you in your prep - knowing why you miss something will help you as you work forward in the q-bank. I think part of the process is self analysis. Best wishes
    PreMed Forum Moderator

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