Chance of being heterozygous in Autosomal Recessive - 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 09-24-2012
USMLE Forums Scout
 
Steps History: Not yet
Posts: 38
Threads: 13
Thanked 9 Times in 4 Posts
Reputation: 19
Genetics Chance of being heterozygous in Autosomal Recessive

30 yrs man is phenotypically normal but two of his siblings died from infantile Tay-Sachs disease autosomal recessive disease that is lethal by 5 years ,, what is the chance that this man is hetrozygous carrier for the disease??

A. 1/4
B. 1/2
C. 2/3
D. 3/4

this Q is in Kaplan note bio .. genetic section.. but i didn't understand even the explanation ...
Reply With Quote Quick reply to this message



  #2  
Old 09-24-2012
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 1,039
Threads: 189
Thanked 557 Times in 318 Posts
Reputation: 567
Default my answer :)

C.2/3

he's normal so he's either dominant homozygous or a carrier. so we're choosing from 3 options. I think that's the main trick here.
Reply With Quote Quick reply to this message
The above post was thanked by:
hassansiraj (09-24-2012), Saiyeda (09-24-2012), venky2600 (09-24-2012)
  #3  
Old 09-24-2012
koolkiller88's Avatar
USMLE Forums Master
 
Steps History: Step 1 Only
Posts: 864
Threads: 62
Thanked 370 Times in 224 Posts
Reputation: 380
Default

As his 2 siblings are affected so we can presume that his both parents were hetrozygous.
So considering that probability (If you consider A- normal and a- affected)
We can have AA- 1, Aa- 2, aa-1 (by punett square)
But as this person is not affected so, aa can't be possibility in this case.

So the person to be hetrozygous is 2/3 (Aa,Aa)/ (AA,Aa,Aa)
__________________
One day i will infect these microbes and they will search for "Anti-MEbiotic"....
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:
hassansiraj (09-24-2012), Janakpriya (09-24-2012), Saiyeda (09-24-2012), step1success (09-24-2012), venky2600 (09-24-2012)
  #4  
Old 09-24-2012
USMLE Forums Addict
 
Steps History: Not yet
Posts: 148
Threads: 26
Thanked 27 Times in 21 Posts
Reputation: 37
Send a message via Skype™ to ashok1
Default

1/4 perhaps
autosomal recessive 25 %
Reply With Quote Quick reply to this message
  #5  
Old 09-24-2012
USMLE Forums Scout
 
Steps History: Not yet
Posts: 38
Threads: 13
Thanked 9 Times in 4 Posts
Reputation: 19
Default

Thank u very much guys u r so helpful....
Reply With Quote Quick reply to this message
  #6  
Old 09-24-2012
USMLE Forums Addict
 
Steps History: Not yet
Posts: 148
Threads: 26
Thanked 27 Times in 21 Posts
Reputation: 37
Send a message via Skype™ to ashok1
Default

I saw the explanation q no 3.... i also do not understand ..genetics is really making me nervous ...
Reply With Quote Quick reply to this message



Reply

Tags
Genetics-, 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
List of Autosomal Recessive Diseases sam88 USMLE Step 1 Bits & Pieces 5 04-26-2013 05:54 PM
Population Genetics; Autosomal Recessive Disease; Probability of affected child? pradeeprox USMLE Step 1 Forum 11 05-17-2012 08:30 AM
Enzyme deficiencies not autosomal recessive? Renaissance USMLE Step 1 Forum 0 05-01-2012 02:59 PM
Fully penetrant autosomal recessive hypermedic USMLE Step 1 Forum 5 04-05-2012 05:10 AM
pregnant woman with autosomal recessive disease sam01 USMLE Step 1 Forum 6 04-15-2010 07:40 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)