namf
Forum Elite
Topics: 80
Posts: 312
|
Hi gang!
Here's trouble (for me anyway).
If you know the prevalence of x-linked recessive Duchenne's is 1/3000 males, what is the gene frequency of this mutation?
1/3000
2/3000
(1/3000) squared
square root of (1/3000)
2 x the square root of 1/3000
DON'T LOOK BELOW IF YOU DON'T WANT TO SEE THE ANSWER :shock:
My reasoning was that if you have a mom giving birth to an affected son, the allelic frequency of which is 1/3000, then she has just doubled the allelic frequency to 2/3000. What's wrong with my thinking (help!).
The Qbank answer: 1/3000
|
| Ahab
Forum Elite
Topics: 9
Posts: 228
|
But if ever one of the unaffected (2999/3000) also had one offspring the allele frequency would be 2/6000 which is 1/3000.
The point of the henderson hasslebach eqn is to show that allele frequency does not change from generation to generation.
|
| cococat
Forum Junior
Topics: 4
Posts: 46
|
if it's XR, then affected male has only one copy of mutated X gene, therefore prevalence of male equals frequency of mutated X gene, so it should also be 1/3000?
|
| adeelmd
Forum Elite
Topics: 40
Posts: 399
|
this is a tricky stupid question because I THINK it's testing BULL instead of medical knowledge... I too guessed 2/3000... but...
the frequency is 1/3000 MALES not 1/3000 TOTAL..
so the frequency in females is also 1/3000,..
when you add the two it's 2/6000 which is 1/3000
(Males do not live long enough to transmit the disease to a daughter, which is why it can only be transmitted by the female, hence the equal incidence)
___________________
where i lay my head is home.
|
| Malaysian
Forum Guru
Topics: 28
Posts: 778
|
The question is good no doubt.It gives the prevalence in MALES as 1/3000...males have XY...and so the gene frequency for the Xrecessive disease is also 1/3000.
Assuming the question said 1/3000in the general population.Would the gene frequency be square root of it then or would the answer be not enough information provided???
|
|
| |
| | | | | |
