Genetics - 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 01-17-2012
USMLE Forums Addict
Steps History: Not yet
Posts: 191
Threads: 96
Thanked 270 Times in 97 Posts
Reputation: 280
Default Genetics

The incidence of a genetic form of diabetes insipidus (MIM*304800) in North Americans was hypothesized to be related to immigration of affected individuals on the ship Hopewell that arrived in Halifax, Nova Scotia several hundred years ago. If the disease allele were known as A, and residents near Halifax had 10 times the frequency of this allele as did those on mainland Canada, which of the following terms best describes this phenomenon?

Selection for allele A

Linkage disequilibrium with allele A

Linkage to allele A

Founder effect for allele A

Assortative mating for allele A
Reply With Quote Quick reply to this message

Old 01-17-2012
Hitman's Avatar
USMLE Forums Master
Steps History: Not yet
Posts: 928
Threads: 17
Thanked 538 Times in 375 Posts
Reputation: 548

Ans D............
Reply With Quote Quick reply to this message
Old 01-18-2012
USMLE Forums Addict
Steps History: Not yet
Posts: 191
Threads: 96
Thanked 270 Times in 97 Posts
Reputation: 280

Founder effects represent a special case of genetic drift in which rare alleles are introduced into a small population by the migration of ancestors. These founder mutant alleles can overcome selective disadvantage because they begin with high frequency in a small gene pool. Linkage disequilibrium describes an association between a particular polymorphic allele and a trait. Many autoimmune diseases exhibit association with particular human leukocyte antigen (HLA) alleles (ie, HLA-B27 and ankylosing spondylitis). The association is not necessarily cause and effect (eg, when viral infections that trigger a disease preferentially infect certain HLA genotypes). Genetic linkage implies physical proximity of the allele locus to the gene causing the disease. Linkage differs from allele association in that either allele A or a may be linked in a given family, depending on which allele is present together with the offending gene. Neither assortative mating (preferential mating by genotype) nor selection (advantageous alleles) applies to the situation under discussion. Later research using DNA polymorphisms has refuted the Hopewell hypothesis, showing that families with this form of diabetes insipidus (MIM*304800) are not related to ancestors from Halifax.
Reply With Quote Quick reply to this message
The above post was thanked by:
doctorFH (01-18-2012), Hitman (01-18-2012), rseruy (12-10-2012), venky2600 (07-11-2012)


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
If you don't die after're done with genetics! Claus_CU USMLE Step 1 Forum 22 02-20-2015 11:19 AM
genetics doxorubicin USMLE Step 1 Forum 7 12-12-2011 12:59 AM
genetics INCOGNITO USMLE Step 1 Forum 4 08-05-2011 09:10 PM
Genetics Question Sandeep USMLE Step 1 Forum 8 04-30-2011 04:44 AM
Genetics, not getting it well Dr. N Elham USMLE Step 1 Forum 3 12-07-2009 06:45 PM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2016 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)