








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 
#1




Calculating the risk of cleft palate for these parents
A male new born at 39 wks gestation has a unilateral cleft lip and palate. studies shown that concordance for this trait in MZ twins 0.40 and DZ twins 0.04. the incidence of cleft lip and palate in general population is 0.001 if the parents of this newborn have a second child the risk for unilateral cleft lip and palate in this child is approximately which?
A) 75% B) 50% C) 25% D) 4% E) 0% hi guys iv got this Q and i need ur help in approaching the correct answer 
#2




Assuming the parents dont have twins (can't really calculate I think), it would be comparing to the General Population where incidence is 1/1000.
I would go with D) 4% I have no idea! 
#3




Quote:
Since the concordance for this trait in DZ twins is 0.04, this should also be for a future child...so I multiplied 0.04*100%... 
The above post was thanked by:  
Claus_CU (05282011) 


#4




Exactly what I did, however i'm still not sure abt the answer..

#5




Quote:

#6




hi guys ...thanks ....i took this question from kaplan q bank and the correct one is 4% ...u r totally correct ,i read the explanation but i didn't get how to approach the correct answer!!!
so we assume that the child would be DZ and we took 100% the general population and multiply 0.04 by 100% ...right? thanks again 
#7




Quote:

The above post was thanked by:  
Amenah (05282011) 
#8




Okay can i know why we didn't use the incidence which is 0.001 and we assume 100% for the general population. thank you again

#9




Quote:
I didnīt use the general population incidence of 1/1000, because this qs. is about a particular family which already have a child with unilateral cleft lip. 
#10




ha Okay i got it ,we just assume it's a DZ and pick the 4% ...thanks Bebix .

#11




Quote:
The risk within the pair of DZ twin should be equal to the risk between two brothers. 
The above post was thanked by:  
Claus_CU (05282011) 
#12




Wow. You guys are seriously good with genetics.

Tags 
Genetics, Step1Questions 
Thread Tools  Search this Thread 
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Genetic Counseling of CF Parents  Claus_CU  USMLE Step 1 Forum  19  07242011 04:40 AM 
Cleft Lip/Palate  apx85  USMLE Step 1 Forum  1  03162011 04:41 PM 
Anterior versus Posterior Cleft Palate  schiwei  USMLE Step 1 Forum  1  12282010 02:39 PM 
cleft palate, microcephaly, and midface hypoplasia  khushboo  USMLE Step 1 Forum  10  09242010 07:57 AM 
Calculating the Pulmonary Vascular Resistance!  doctorF  USMLE Step 1 Forum  3  07122010 02:04 PM 
