loss of ampicillin resistance in E. coli - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
Home
USMLE Articles
USMLE News
USMLE Polls
USMLE Books
USMLE Apps
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


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 04-24-2010
Seetal's Avatar
USMLE Forums Master
 
Steps History: Step 1 Only
Posts: 919
Threads: 134
Thanked 1,301 Times in 364 Posts
Reputation: 1324
Send a message via MSN to Seetal
Microscope loss of ampicillin resistance in E. coli

Escherichia coli strains X and Y are both resistant to ampicillin. Ampicillin resistance is stable in strain X when it is grown for multiple generations in the absence of the antibiotic. However, strain Y loses ampicillin resistance when it is grown in media without the antibiotic. Which of the following best explains the acquisition of ampicillin susceptibility in strain Y?

(A) Downregulation of the resistance gene
(B) Insertion of a transposon into the resistance gene
(C) Loss of a plasmid carrying the resistance gene
(D) Point mutations in the resistance gene
(E) Recombination with a defective copy of the resistance gene
Reply With Quote Quick reply to this message
The above post was thanked by:
aungawa (04-25-2010)



  #2  
Old 04-24-2010
USMLE Forums Scout
 
Steps History: Not yet
Posts: 69
Threads: 16
Thanked 45 Times in 21 Posts
Reputation: 83
Send a message via Yahoo to mosallam Send a message via Skype™ to mosallam
Default

i think it is (E) Recombination with a defective copy of the resistance gene
Reply With Quote Quick reply to this message
  #3  
Old 04-25-2010
HouseWannabe's Avatar
USMLE Forums Addict
 
Steps History: 1 + CS
Posts: 120
Threads: 13
Thanked 146 Times in 45 Posts
Reputation: 156
Default C

From what I can remember, resistance is carried by plasmids, so if you lose the plasmids, you lose the resistance.
Reply With Quote Quick reply to this message
  #4  
Old 04-26-2010
USMLE Forums Scout
 
Steps History: Not yet
Posts: 73
Threads: 7
Thanked 40 Times in 21 Posts
Reputation: 60
Default

Should be C.
Reply With Quote Quick reply to this message
  #5  
Old 04-27-2010
Seetal's Avatar
USMLE Forums Master
 
Steps History: Step 1 Only
Posts: 919
Threads: 134
Thanked 1,301 Times in 364 Posts
Reputation: 1324
Send a message via MSN to Seetal
Default

yes u're ryte. the answer is C. resistance is carried by plasmids. lose the plasmid, lose the resistance!
Reply With Quote Quick reply to this message



Reply

Tags
Microbiology-, Step-1-Questions

Quick Reply
Message:
Options

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:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
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.
Location
Where you live. Leave blank if you don't want to tell.

Log-in

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
E. coli Lactose Metabolism DocSikorski USMLE Step 1 Forum 13 08-18-2012 06:51 PM
treatment difference between E Coli O157:H7 and Shigella chienpolska USMLE Step 2 CK Forum 1 11-12-2011 02:16 AM
E. coli septisemia in Infant sayid USMLE Step 1 Buzzwords 1 09-11-2011 08:13 AM
E. coli Mnemonic Seetal USMLE Step 1 Mnemonics 4 03-28-2010 11:23 PM
E. coli Virulence factors DrSeddik USMLE Step 1 Bits & Pieces 0 11-30-2009 02:12 PM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 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)