genetics que - kaur

[ArchivalUser]

frequency of the most common mutation, K304E,causing AR medium chain acyl CoA DEHYDROGENASE DEFICENCY IN USA POPULATION IS 0.77%{1/130} WHT IS THE APPROXIMATE PREDICTIVE VALUE OF HOMOGYGOTESITY for the K304E mutation in usa population ?
a 1/65
b 1/260
c 1/6500
d 1/17,000
e 1/21,000

plzzz ans with explation .wht is 1/130 and how ?

[ArchivalUser]

This Q stem told you that q=0.77%=1/130, they are asking qxq=(1/130)^2=1/16900, so D is the closest answer.

[ArchivalUser]

hi danille

i know u give rsponce of my ans bcoz u did same ques like this before .but i confused with q and q2.plzzz xplan me in detail thanks in advance plzzzzzzz gl

[ArchivalUser]

why it is q ?i did not understand .

[ArchivalUser]

Did you read my post here about understanding H-W equation? It is here:

http://usmleforum.com/forum/message.php?id=53819

definitions:
p and q are gene frequencies. In this Q, they already told you that 0.77% is the frequency of one certain gene ,called K304E. We don't care about the name of the gene. We care about the fact that its frequency in the population is 0,77%, by definition, it is the value of q.

Understand?

Okay, now you know the gene frequency is 0.77%, they are asking for the phenotype: homologous K304E, to be homologous, both allele have to be K304E , right? Otherwise they won't be homologous K304E, so they are asking for q^2.

To help you understand this kind of Q, you have to know, that on chromosomes, different genes normally have two alleles, they can be the same , or different. For the same ones, they are either homologous normal or homologous diseased, for the different ones, they are just carriers of that certain disease.