Test your knowledge #29! (Molecular biology) - 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 03-20-2011
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 590
Threads: 31
Thanked 1,230 Times in 411 Posts
Reputation: 1254
Arrow Test your knowledge #29! (Molecular biology)

An 18-year-old lifeguard sits in the sun all day wearing only a swimsuit, a t-shirt, and sunglasses. As UV-B rays damage the DNA of the squamous cells on the lifeguard’s ear, which of the following steps is the first to occur?
  1. BAX gene transcription is activated
  2. Cyclin/CDK complex is inhibited
  3. GADD45 transcription is stimulated
  4. p21 transcription is stimulated
  5. p53 degradation is halted and the enzyme is modified
Reply With Quote Quick reply to this message
The above post was thanked by:
aktorque (03-20-2011), doc_study (03-21-2011), DoctorB (03-20-2011), donofitaly (03-20-2011), dr_lizard (09-06-2011), struggle (03-20-2011)



  #2  
Old 03-20-2011
chulady's Avatar
USMLE Forums Addict
 
Steps History: 1+CK+CS+3
Posts: 198
Threads: 56
Thanked 54 Times in 33 Posts
Reputation: 64
Smile D

D. p21 transcription is stimulated
Reply With Quote Quick reply to this message
The above post was thanked by:
aktorque (03-20-2011), Mondoshawan (03-20-2011)
  #3  
Old 03-20-2011
USMLE Forums Addict
 
Steps History: Step 1 Only
Posts: 161
Threads: 11
Thanked 378 Times in 106 Posts
Reputation: 388
Default

Hmm not too sure but I'm going to go with squamous cell carcinoma...

E - p53
Reply With Quote Quick reply to this message
The above post was thanked by:
aktorque (03-20-2011), Mondoshawan (03-20-2011)
 
  #4  
Old 03-20-2011
USMLE Forums Scout
 
Steps History: Not yet
Posts: 59
Threads: 15
Thanked 30 Times in 19 Posts
Reputation: 40
Default

I'd go with p21. It regulates p53.
Reply With Quote Quick reply to this message
The above post was thanked by:
aktorque (03-20-2011), Mondoshawan (03-20-2011)
  #5  
Old 03-20-2011
USMLE Forums Scout
 
Steps History: Not yet
Posts: 15
Threads: 7
Thanked 6 Times in 3 Posts
Reputation: 16
Default

I will go with E... p53
Reply With Quote Quick reply to this message
The above post was thanked by:
aktorque (03-20-2011), Mondoshawan (03-20-2011)
  #6  
Old 03-20-2011
USMLE Forums Guru
 
Steps History: 1 + CS
Posts: 405
Threads: 55
Thanked 528 Times in 155 Posts
Reputation: 538
Default

E. p53 degradation is halted and the enzyme is modified?

We are speaking of squamous cell carcinoma i think here.

BAX gene transcription is activated - I don't think they undergo apoptosis which would be the result of BAX genes.
Cyclin/CDK complex is inhibited - this may eventually happen but p53 degradation is halted and enzyme is modified first (which is what the question is asking).
GADD45 transcription is stimulated - i have no idea what is this.
p21 transcription is stimulated - i have no idea what is this.
Reply With Quote Quick reply to this message
The above post was thanked by:
aktorque (03-20-2011), bronchiole (03-20-2011), doc_study (03-21-2011), Mondoshawan (03-20-2011)
  #7  
Old 03-20-2011
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 590
Threads: 31
Thanked 1,230 Times in 411 Posts
Reputation: 1254
Correct Answer E is correct!

The correct answer is E. p53 degradation is halted and the enzyme is modified.

In response to DNA damage or other types of stress, the N-terminal end of p53 is phosphorylated, disrupting the binding of Mdm2, an inhibitor of p53 and an ubiquitin ligase. With less Mdm2 binding, more p53 remains in the nucleus and its half-life increases. The C-terminal end is also acetylated by transcriptional coactivators, further promoting p53’s regulatory activity. p53 stimulates the transcription of the genes producing GADD45 (C) and p21 (D). p21 block’s cyclin/CDK’s (B) phosphorylation of Rb, so E2F remains inhibited and progression through the cell cycle is halted. If the damage is repaired, Mdm2 (whose transcription is also stimulated by p53) will eventually regain control over p53 levels. If the damage is not repaired, p53 will promote both transcription and activation of Bax, the pro-apoptotic Bcl-2 protein (A).

I couldn't find just the right illustration - anyone have a good one? Here's a simple one from wikipedia:

Test your knowledge #29! (Molecular biology)-p53_pathways.jpg
click image to enlarge
Reply With Quote Quick reply to this message
The above post was thanked by:
abeer (02-19-2013), aktorque (03-20-2011), bronchiole (03-20-2011), chulady (03-20-2011), doc_study (03-21-2011), donofitaly (03-21-2011), dr_lizard (09-06-2011), rah_mem (03-22-2011), Sana Zahid (04-19-2011), struggle (03-20-2011)
  #8  
Old 03-20-2011
USMLE Forums Addict
 
Steps History: Step 1 Only
Posts: 161
Threads: 11
Thanked 378 Times in 106 Posts
Reputation: 388
Default

Yay!! woohoooo
Reply With Quote Quick reply to this message
  #9  
Old 03-20-2011
USMLE Forums Guru
 
Steps History: Not yet
Posts: 324
Threads: 70
Thanked 238 Times in 144 Posts
Reputation: 248
Default

so it means that all of the processes occur but secondary to halting of p53 degradation..right?
Reply With Quote Quick reply to this message
The above post was thanked by:
Mondoshawan (03-20-2011)
  #10  
Old 03-20-2011
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 590
Threads: 31
Thanked 1,230 Times in 411 Posts
Reputation: 1254
Default

Quote:
Originally Posted by struggle View Post
so it means that all of the processes occur but secondary to halting of p53 degradation..right?
Precisely!
Reply With Quote Quick reply to this message
The above post was thanked by:
struggle (03-20-2011)
  #11  
Old 03-20-2011
USMLE Forums Guru
 
Steps History: Not yet
Posts: 324
Threads: 70
Thanked 238 Times in 144 Posts
Reputation: 248
Default

good question..keep it up..
Reply With Quote Quick reply to this message
The above post was thanked by:
Mondoshawan (03-20-2011)



Reply

Tags
Figures-, 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
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
How do I improve Neuroanatomy and Molecular Biology. struggle USMLE Step 1 Forum 4 02-25-2011 09:02 PM
Test your knowledge #7! (Molecular Biology Techniques) Mondoshawan USMLE Step 1 Forum 6 02-10-2011 09:34 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)