destroyer bio 228

[pistolpete007]

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a certain autosomal recessive condition is srrn in approximately 1/50 people, but are symptoms-free. if a male and female are both carriers of the gene, what is the probability they have a diseased child

...the way i see it is that the male and female are heterozygotes.....so therefore there should be 25% chace of having a diseased child...AO A x AO A= 25%AOAO 50%AOA and 25%A.....but the answer is .01%...the way they did it was 1/50=.02 sooo .02 x .02 x 25 = .01%....why did they do this? we already know that the parents are heterozygotes there for the chance of them getting a child should be 25% regaurdless of whatever overall percent is because they are asking what is the probability that THEY HAVE A diseased child.

 

[Orgodox]

Because the other 98 percent can have the defected gene but be symptom free so not only does the kid have to get the genes but he needs to have thr symptom

 

[Christmasskunk]

why times .02 twice?

 

[Mstoothlady2012]

why Times .02 Twice?

0.02 = 2% =1/50

 

[Christmasskunk]

0.02 = 2% =1/50

Right I understand that, but why do you have times .02 twice with 25 to get the answer? .02 x .02 x 25 = .01

..... ????? ???? ????

 

[Mstoothlady2012]

i don't really understand why we have to do that. But even after multiplying by 0.02 twice I get 0.01% which is answer choice D not C.

 

[loanne]

yeah i didn't understand this problem either. The only way it makes sense to me is if the question was asking what the probability two parents would have a diseased child--and didnt say that they were known to be heterozygous...

I also dont really understand how "not showing symptoms" comes into play. The problem says that 1/50 have the disease, but dont show symptoms, right? in that case, why does it matter in solving the problem--the kid would have the disease even if he didnt show symptoms.

confused.

 

[mddang]

I was staring at this question yesterday too!

This question is kind of messed up because it states specifically that BOTH parents are carriers of the gene.
Because both parents are carriers, the chance of them producing a diseased child is 25%.


However, the explanation is worded as if the two parents were chosen at random.
The probability of a male carrying the allele is 1/50 (or 2%) and the chance of the female carrying the allele is 1/50.

The chance of the male and the female carrying the allele is (.02)(.02), which equals .0004.

The chance of both of the male and the female passing on this allele is .25.


(.0004)(.25) = .0001 = .01%


The question is worded incorrectly..