Molecular Biology of abetalipoproteinemia; abstract based question - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
USMLE Articles
Go Back   USMLE Forums > USMLE Step 1 Forum

USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam

Thread Tools Search this Thread Display Modes
Old 11-10-2011
USMLE Forums Addict
Steps History: Not yet
Posts: 191
Threads: 96
Thanked 270 Times in 97 Posts
Reputation: 280
Molecular Molecular Biology of abetalipoproteinemia; abstract based question

Lipoproteins transport lipids from intestine and liver where they are absorbed and metabolized to peripheral tissues via the bloodstream. They contain core proteins (apo proteins) that bind various types of lipid, thus producing lipoprotein complexes of varying densities—very low density lipoproteins (VLDL), low density lipoproteins (LDL), and high density lipoproteins (HDL) after plasma lipoprotein electophoresis. A disorder called abetalipoproteinemia (200100) was distinguished by its deficiency of the bands for very low density lipoproteins (VLDL) and low density lipoproteins (LDL) after plasma electrophoresis. Affected patients have ataxia (wide gait, incoordination), retinopathy (retinal degeneration with blindness), and myopathy (muscle weakness). VLDL and LDL contain the same apoB core protein, their different densities produced by association with different lipids, and apoB became good candidate for mutation in the disorder. Initial characterization of the apoB gene together with its mRNA and protein products demonstrated identical mRNA sizes in all tissues. Western blotting using antibody specific for the amino-terminus of apoB protein showed a 100-kDa species in liver and a 48-kDa species in intestine, as did antibody specific for the C-terminus of the 48-kDa intestinal protein. Molecular study of a patient with abetalipoproteinemia showed normal mRNA sizes, but 100-kDa peptide species were identified in both liver and intestine using the amino or carboxy-terminus antibody probes. Which of the following processes is most likely deficient in this patient with apobetalipoproteinemia?

A. RNA splicing
B. DNA amplification
C. Transcription initiation
D. Transcription factor phosphorylation
E. RNA editing

During the analyses described in the previous question, another patient with abetalipoproteinemia was found to have negligible amounts of apoB protein in either liver or intestine. Analysis of the patient's DNA and RNA would most likely yield which of the following results?

A. Substitution of the last base of a codon near the middle of the first apoB exon
B. Insertion of two bases near the apoB amino terminus
D. Transversion producing a nonsense mutation within the first apoB intron
C. Transition affecting the thirtieth base of the first apoB intron
E. Base substitution changing glycine for alanine near the apoB carboxyl terminus
Reply With Quote Quick reply to this message

Old 11-10-2011
dr.muhamad's Avatar
USMLE Forums Guru
Steps History: 1 + CS
Posts: 302
Threads: 22
Thanked 97 Times in 62 Posts
Reputation: 107

first question is A
the other idk
Reply With Quote Quick reply to this message
Old 11-11-2011
USMLE2011m's Avatar
USMLE Forums Veteran
Steps History: Step 1 Only
Posts: 277
Threads: 36
Thanked 157 Times in 95 Posts
Reputation: 167

1. A
2. A as well.
Set your mind to it, and you will be there.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message


Molecular-Biology-, Step-1-Questions

Quick Reply

Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

Favorite USMLE Books
What USMLE books you really think are useful. Leave blank if you don't want to tell.
Where you live. Leave blank if you don't want to tell.


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Similar Threads
Thread Thread Starter Forum Replies Last Post
Cell Biology Histology & Molecular Biology references? Arma USMLE Step 1 Forum 2 04-29-2016 01:56 AM
Two Molecular Biology Doubts! Androide89 USMLE Step 1 Forum 14 07-27-2014 08:53 AM
Complementary DNA Strands! struggle USMLE Step 1 Forum 1 04-11-2012 03:54 AM
Molecular Biology Q drgsarunprasath USMLE Step 1 Forum 4 08-11-2011 03:59 AM
molecular biology question usmlemydream USMLE Step 1 Forum 14 07-30-2011 07:05 AM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2014)