sk
Forum Senior
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Five percent of individuals of a particular population are known to carry a recessive gene for poliodystrophy, an inherited disorder characterized by the onset of recurrent seizures and dementia early on in childhood. A 32 year old woman who had a brother with this disease seeks genetic counselling . The patient's husband. is an only child and does not know if his family had a history of this disorder. What is the probability that this patient is a carrier of poliodystrophy?
a.1/20
b.1/10
c.3/8
d.2/3
e.3/4
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| usmleasr
Forum Guru
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her brother has the disease implies both of her parents r carriers..
so she can be eithe normal or carrier ...only 2 possiblities..
so probablity is 2/3 :roll:
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| asmi
Forum Hero
Topics: 1043
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iam also thinking in terms of 2/3....but we have to consider that 5 % population thing..
:cry: why don't i understand it...very bad of myself.. :cry:
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| sk
Forum Senior
Topics: 23
Posts: 122
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Both of you...well done!.....the answer is D...2/3...i got it right too......but it was a difficult question...and the answer is even more confusing....
Well.......... the 32 year old woman had a brother with the disease which means that the parents were heterozy carriers.....Now that means...the woman can either be a genotypically normal homzyg or a hetero carrier like her parents.....
So probability that she is a healthy homozy is 3/4.....and the probability that she is a carrier is 1/2
so probability of being just a carrier = 1/2 / 3/4
=2/3
confusing answer?...
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| asmi
Forum Hero
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thanks for the explanation
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| dyk33
Forum Newbie
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what would be the chance of the child being affected by this disease?
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| asmi
Forum Hero
Topics: 1043
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i think there will be 25% chance of having normal / affected child.
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| crista
Forum Guru
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Posts: 408
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are you sure?
what about:
2/3 (for mother) * 5/100 (for father)=1/30?
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| dyk33
Forum Newbie
Topics: 7
Posts: 29
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if the disease is AR,
chances of
mom being a carrier 2/3
father being a carrier 5/100
mom passing the gene 2/3 x 1/2 = 1/3
father passing the gene 5/100 x 1/2 = 5/200
thus the kid being affected 1/3 x 5/200 = 5/600 = 1/120
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