Fragile X Syndrome - 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 08-18-2010
ashishkabir's Avatar
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 625
Threads: 19
Thanked 374 Times in 221 Posts
Reputation: 394
DNA Fragile X Syndrome

Hello all... So there's this UWorld question which asks - and I'm paraphrasing here after analyzing the question to get the diagnosis - what is the mechanism of the symptoms in Fragile X syndrome... So I, having done First Aid, argue - oh - many CGG repeats make the chromosome "fragile" and, as it says in FA 2010 (Associated with chromosome breakage - p87) I choose the "DNA damage" or whatever option there was similar to that. Wrong!!!! Apparently the answer is DNA Methylation. FA's comment on this on the same block is "X-linked defect affecting the methylation and expression of the FMR-1 gene" I wish I could extrapolate from that somehow that what FA meant was ohh - yeah if there are a lot of cysteine (from the extra CGG) residues then they get methylated and then this methylation inactivates the whole FMR gene so no transcription occurs so you get the symptoms. That my friends, is how Fragile X works... I am soo going to fail...
Reply With Quote Quick reply to this message
The above post was thanked by:
Priyanka (10-25-2013), samajade (08-21-2016), Usmle16Forall (02-18-2017)



  #2  
Old 08-18-2010
S.Martin's Avatar
USMLE Forums Scout
 
Steps History: Not yet
Posts: 34
Threads: 3
Thanked 21 Times in 12 Posts
Reputation: 31
Unhappy

Oh my God,

Don't tell me that we'll see such questions in the exam

Please tell me the percentage of folks who got that question right in UW
Reply With Quote Quick reply to this message
The above post was thanked by:
Usmle16Forall (02-18-2017)
  #3  
Old 08-18-2010
ashishkabir's Avatar
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 625
Threads: 19
Thanked 374 Times in 221 Posts
Reputation: 394
Default

29% so maybe that says something - still...
Reply With Quote Quick reply to this message
The above post was thanked by:
Usmle16Forall (02-18-2017)
 
  #4  
Old 08-18-2010
doctorF's Avatar
USMLE Forums Guru
 
Steps History: Not yet
Posts: 316
Threads: 68
Thanked 407 Times in 110 Posts
Reputation: 427
Default this is what HY GENETICS has to say!!!

fragile X is an X-linked recessive disorder caused by a 200-1000 + unstable repeat sequences of CGG outside the FMR1 gene on chromosome X for FMRProtein1, which is a nucleocytoplasmic shuttling protein binding several MRNAs found abunduntly in neurons. the 200-1000+ unstable repeat sequences of CGG creates a fragile site. this has also been associated with hypermethylation of FMR1 gene so that FMRP1 is not xpressed.

moreover it says that that there are 2 sites A which involves a 200-100+ unstable repeat sequence of CGG located in 5' untranslated region in FMR and site B that involves 200+ repeat sequences on FMR gene
__________________
Why does Good luck often carries more weightage than hard work in successes???
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
The above post was thanked by:
bebix (04-22-2011), Learner (01-10-2012), Usmle16Forall (02-18-2017)
  #5  
Old 08-21-2010
Haisook's Avatar
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 752
Threads: 124
Thanked 615 Times in 265 Posts
Reputation: 635
Default

Btw, also in Huntington disease, the mechanism of damage is hypermethylation.

UW mentions that hypermethylation causes a so-called transcriptional silencing by hiding the DNA from the transcription factors.

Acetylation, on the other hand, exposes the DNA further, leading to the opposite; more transcription.
Reply With Quote Quick reply to this message
The above post was thanked by:
im99 (02-20-2011), riya10 (08-03-2011), Usmle16Forall (02-18-2017)
  #6  
Old 08-21-2010
ashishkabir's Avatar
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 625
Threads: 19
Thanked 374 Times in 221 Posts
Reputation: 394
Default

Thanks DoctorF and Haisook. Questions like this are more fundamental than just memorizing a fact since it is more a detail about a concept. It scares me that after all this time I'm still having trouble with concepts...
Reply With Quote Quick reply to this message
The above post was thanked by:
doctorF (08-22-2010), Usmle16Forall (02-18-2017)
  #7  
Old 08-21-2010
Haisook's Avatar
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 752
Threads: 124
Thanked 615 Times in 265 Posts
Reputation: 635
Default

Quote:
Originally Posted by ashishkabir View Post
Thanks DoctorF and Haisook. Questions like this are more fundamental than just memorizing a fact since it is more a detail about a concept. It scares me that after all this time I'm still having trouble with concepts...
It seems we'll never stop learning until the last minute
Reply With Quote Quick reply to this message
The above post was thanked by:
Usmle16Forall (02-18-2017)



Reply

Tags
Genetics-, Molecular-Biology-, Syndromes-Acronyms

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
fragile X ques doctorF USMLE Step 1 Forum 13 09-16-2016 06:51 PM
Inheritance of Fragile X Syndrome Sha6ir USMLE Step 1 Forum 4 06-07-2011 08:51 PM
Man In Barrel Syndrome versus Locked In Syndrome Androide89 USMLE Step 1 Forum 7 12-04-2010 10:47 PM
Fragile X Syndrome lee-usmle USMLE Step 1 Buzzwords 2 11-29-2010 10:55 AM
Differentiating Staphylococcal Scalded Skin Syndrome from Toxic Epidermal Necrolysis and Steven Johnson Syndrome lee-usmle USMLE Step 2 CK Bits & Pieces 0 03-21-2010 06:12 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)