doesn't have this condition, asks about the risk that her own children will be affected. The best probabble estimate:

A) near zero

B) 1/2

C) 1/4

D) 1/8

E) 1/16

F) 1/32

1 - 11 of 11 Posts

doesn't have this condition, asks about the risk that her own children will be affected. The best probabble estimate:

A) near zero

B) 1/2

C) 1/4

D) 1/8

E) 1/16

F) 1/32

Joined

·
625 Posts

Can someone show me what I'm missing?

if this is the only info given in the questn we can safely assume that they are talking abt vw disease and not haemophilia because prevalence of vw is 1/100 in US population,while for hamophilia which is much rarer its 1/10,000....

and VW-A being more common,it is inherited in autosomal domnant fashion... so ans may be 1/2....pls correct me if am wrong..:notsure:

I am assuming its hemophillia A because:

sister is not affected (more likely X-linked)

hemoarthorsis is present

If that is the case... the patient's mother must be a carrier (father cannot pass down to affected son)

The patient's mother has a 50% chance of passing the mutated X chromsome to the patient's sister

Now if the sister has a daugther... there is 50% chance that she will give her defected gene but this will be masked (unless unfavourable lyonisation occurs). If the sister has a son...ther is a 50% chance that she will giver defected X chrmosome and since the father gives a Y... the son will have hemophillia.

So we are dealing with two dependent events: the likely hood of having an affected child (1/4) if she is a carrier (1/2) = 1/8

it is hemophilia and as u know it is x linked disease ..so if brother is having disease and she doesnt that means most likely her mother is carier and father normal.. so she has 1/2 chance of being a carrier as when u cross carier mother of this girl with normal father one girl is normal and other is carrier so =1/2

now if she mates with normal male as she should coz its not mention of her husband so out of 2 gals and 2 boys only one boy will be diseased ..so = 1/4!

so probability of her children will be 1/2 * 1/4 =1/8

1 - 11 of 11 Posts

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