Why stem cells not proliferating here? - 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 06-08-2013
USMLE Forums Scout
Steps History: ---
Posts: 57
Threads: 30
Thanked 15 Times in 11 Posts
Reputation: 25
Show Teeth Why stem cells not proliferating here?

Dyskeratosis congenital (DKC) is a genetically inherited disease in which the proliferative capacity of stem cells is markedly impaired. The defect has been traced to inadequate production of an enzyme needed for chromosome duplication in the nuclei of rapidly dividing cells.
Structural analysis has shown that the active site of this protein contains a single-stranded RNA that is required for normal catalytic function. Which step in DNA replication is most likely deficient in DKC patients?
A. Synthesis of centromeres
B. Synthesis of Okasaki fragments
C. Synthesis of RNA primers
D. Synthesis of telomeres
E. Removal of RNA primers

plz give expln. similar q may appear in exam imo, what say ?
Reply With Quote Quick reply to this message
The above post was thanked by:
dr mumble (07-04-2013)

Old 06-08-2013
USMLE Forums Scout
Steps History: Not yet
Posts: 32
Threads: 6
Thanked 66 Times in 18 Posts
Reputation: 76

Ans is D. Synthesis of telomeres.

DKC is a very rare congenital condition about 1 in a million so doubt it would come up. But hey as goljan says, now you know!

There are two types, Autosomal dominant which is associated with mutation in TERC (telomerase RNA component), while X-linked DKC is due to mutation in gene for dyskerin, involved in telomerase function as well.

The key point to note is that there is a mutation that affects TERC levels, which affects the normal function of telomerase, which maintains the telomeres. Remember telomerase preserves or protects the length of the telomeres (sequence of nontranscribed DNA at ends of chromosomes). So DNA would be prone to damage and so resulting in chromosome instability.

Source pubmed. (can't post the link so google DKC pubmed)

Hope that helps.
Reply With Quote Quick reply to this message
The above post was thanked by:
dr mumble (07-04-2013), shoty (06-08-2013)


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
Brain Stem Lesion lee-usmle USMLE Step 1 Forum 9 06-10-2014 04:57 PM
Transgenic mouse and gene insertion in fertilized eggs versus stem cells? usluipek USMLE Step 1 Forum 4 02-20-2013 08:44 AM
Hair Stem Cells! venky2600 USMLE Step 1 Forum 4 10-07-2012 08:19 PM
Verapamil effects on nodal cells or ventricular cells? kenlee USMLE Step 1 Forum 1 04-04-2012 12:48 AM
cells that arise from arachnoid cells ricko335 USMLE Step 1 Forum 6 09-13-2011 07:11 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)