DNA Southern Blotting Question! - 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 06-22-2012
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 1,039
Threads: 189
Thanked 561 Times in 319 Posts
Reputation: 571
DNA DNA Southern Blotting Question!

mRNA encoding glucose 6-phosphate was isolated from baboon liver and used to make a 32P-cDNA probe. DNA was then isolated from marmoset and from human tissue, digested with a restriction endonuclease, Southern blotted, and probed with the 32P-cDNA. Which of the following conclusions can be drawn from the results of this analysis shown in the picture (see attachment):

a) The glucose 6-phosphate gene is present in baboon, marmoset and human liver
b) Both marmoset and human liver express glucose 6-phosphate gene
c) The are two glucose 6-phosphate genes in the human liver
d) The glucose 6-phosphate gene is on different chromosomes in the marmoset and in the human
e) The human and marmoset tissue used in this experiment is from liver



To those of you who will read this question and think 'wtf?' (at least that was my first reaction ), please read it again and believe me it's not a hard question, it's just put this way to make us believe it is hard. This q tests understanding of the concept behind used technique.

DNA Southern Blotting Question!-question.jpg
Click image to enlarge
Reply With Quote Quick reply to this message



  #2  
Old 06-22-2012
numbndumb's Avatar
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 529
Threads: 57
Thanked 283 Times in 151 Posts
Reputation: 293
Default

A) The glucose 6-phosphate gene is present in baboon, marmoset and human liver
__________________
I've become so numb
Reply With Quote Quick reply to this message
  #3  
Old 06-22-2012
USMLE Forums Scout
 
Steps History: 1+CK+CS
Posts: 40
Threads: 1
Thanked 51 Times in 16 Posts
Reputation: 61
Default

The answer is probably A, because the probe formed from the baboon cDNA can bind to both the human and marmoset genes the only difference being RFLPs.
Reply With Quote Quick reply to this message
 
  #4  
Old 06-22-2012
Guest
 
Steps History: ---
Posts: 197
Threads: 9
Thanked 98 Times in 64 Posts
Reputation: 108
Default

How can an mRNA encode glucose-6-phosphate? do you mean glucose6phosphotase?

My answer is A. It cant be B since you said DNA, not entire cell extract.
Reply With Quote Quick reply to this message
The above post was thanked by:
Casandra (06-22-2012)
  #5  
Old 06-22-2012
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 1,039
Threads: 189
Thanked 561 Times in 319 Posts
Reputation: 571
Default .

Quote:
Originally Posted by smanthrav View Post
How can an mRNA encode glucose-6-phosphate? do you mean glucose6phosphotase?

My answer is A. It cant be B since you said DNA, not entire cell extract.
yes, it should be glucose 6-phosphotase!! thanks for pointing that out!
I pasted it and didn't notice..
Reply With Quote Quick reply to this message
  #6  
Old 06-22-2012
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 1,039
Threads: 189
Thanked 561 Times in 319 Posts
Reputation: 571
Default correct answer :)

Correct answer is a) The glucose 6-phosphate gene is present in baboon, marmoset and human liver

Reply With Quote Quick reply to this message
  #7  
Old 06-23-2012
Kabutar111's Avatar
USMLE Forums Guru
 
Steps History: Not yet
Posts: 414
Threads: 30
Thanked 87 Times in 70 Posts
Reputation: 97
Send a message via Skype™ to Kabutar111
Default

Quote:
Originally Posted by Zamalek View Post
The answer is probably A, because the probe formed from the baboon cDNA can bind to both the human and marmoset genes the only difference being RFLPs.
How do you know that probe baboon binds both when it is even not represented ?
What I am missing here ?


Sent from my iPhone using Tapatalk
__________________
There is no shortcut to SUCCESS ,and there is no excuse for FALIURE - by Kabutar111
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
  #8  
Old 06-23-2012
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 1,039
Threads: 189
Thanked 561 Times in 319 Posts
Reputation: 571
Default .

Quote:
Originally Posted by Kabutar111 View Post
How do you know that probe baboon binds both when it is even not represented ?
What I am missing here ?


Sent from my iPhone using Tapatalk
it's not presented in the attachment but it's mentioned in the stem:
"mRNA encoding glucose 6-phosphatase was isolated from baboon liver and used to make a 32P-cDNA probe."
Reply With Quote Quick reply to this message
  #9  
Old 06-23-2012
Kabutar111's Avatar
USMLE Forums Guru
 
Steps History: Not yet
Posts: 414
Threads: 30
Thanked 87 Times in 70 Posts
Reputation: 97
Send a message via Skype™ to Kabutar111
Default

Quote:
Originally Posted by Casandra View Post
it's not presented in the attachment but it's mentioned in the stem:
"mRNA encoding glucose 6-phosphatase was isolated from baboon liver and used to make a 32P-cDNA probe."
But if it's not in attachment how we even know where the probe will be located in attachment , I mean maybe none of them aligned With first animal??


Sent from my iPhone using Tapatalk
__________________
There is no shortcut to SUCCESS ,and there is no excuse for FALIURE - by Kabutar111
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
  #10  
Old 06-23-2012
Kabutar111's Avatar
USMLE Forums Guru
 
Steps History: Not yet
Posts: 414
Threads: 30
Thanked 87 Times in 70 Posts
Reputation: 97
Send a message via Skype™ to Kabutar111
Default

??confused
__________________
There is no shortcut to SUCCESS ,and there is no excuse for FALIURE - by Kabutar111
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
  #11  
Old 06-23-2012
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 1,039
Threads: 189
Thanked 561 Times in 319 Posts
Reputation: 571
Default .

Quote:
Originally Posted by Kabutar111 View Post
But if it's not in attachment how we even know where the probe will be located in attachment , I mean maybe none of them aligned With first animal??


Sent from my iPhone using Tapatalk
it's true that it is not showed directly in the picture (attachment) which band represents the probe BUT when you read all the alternatives given you will notice they make us assume the upper band is the one they are talking about (probe-binding site).
The other options don't make sense as this test here doesn't tell us anything about gene location on chromosome(s) (option D), nor where those tissues are from (option E). Based on the stem and picture we can't tell either how many genes there are either in human or marmoset DNA.
We are left with A and B. But given the first line of the stem: "mRNA encoding glucose 6-phosphate was isolated from baboon liver and used to make a 32P-cDNA probe.", option B would be incomplete so A is correct.

Hope that helps
Reply With Quote Quick reply to this message
The above post was thanked by:
DefeatTheBeast (06-23-2012), Kabutar111 (06-23-2012)
  #12  
Old 06-23-2012
Kabutar111's Avatar
USMLE Forums Guru
 
Steps History: Not yet
Posts: 414
Threads: 30
Thanked 87 Times in 70 Posts
Reputation: 97
Send a message via Skype™ to Kabutar111
Default

Quote:
Originally Posted by Casandra View Post
it's true that it is not showed directly in the picture (attachment) which band represents the probe BUT when you read all the alternatives given you will notice they make us assume the upper band is the one they are talking about (probe-binding site).
The other options don't make sense as this test here doesn't tell us anything about gene location on chromosome(s) (option D), nor where those tissues are from (option E). Based on the stem and picture we can't tell either how many genes there are either in human or marmoset DNA.
We are left with A and B. But given the first line of the stem: "mRNA encoding glucose 6-phosphate was isolated from baboon liver and used to make a 32P-cDNA probe.", option B would be incomplete so A is correct.

Hope that helps
As always very explanatory and helpful .thanks


Sent from my iPhone using Tapatalk
__________________
There is no shortcut to SUCCESS ,and there is no excuse for FALIURE - by Kabutar111
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



Reply

Tags
Figures-, Genetics-, Molecular-Biology-, 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
Gel electrophoresis vs. Southern blot kenlee USMLE Step 1 Forum 4 01-27-2015 11:59 PM
Looking for CS Partner in Northern MA or Southern NH; Exam: April 2012 cateye USMLE Step 2 CS Study Partners 1 03-22-2012 10:01 AM
I have a Room - Place Is Close To LA Downtown / University Of Southern California vijidoc62 Sharing Rooms & Housing 0 06-16-2010 10:42 AM
Blotting Technique! sam01 USMLE Step 1 Forum 6 04-16-2010 06:14 PM
Northern vs Southern vs Western Blot - HELP! tima USMLE Step 1 Forum 5 12-21-2009 11:06 AM

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)