reet
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A man and woman are both affected by an autosomal dominant disorder that is lethal in the embryonic period in homozygotes. The disease has 50% penetrance in heterozygotes. On average, what proportion of their live-born offspring will be affected?.
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| msyamp
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66%
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| robin082006
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=2/3*1/2 = 1/3
a live born baby has 2/3 chance of Aa
50% penetrance--> 1/3 phenotypic baby
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| reet
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yep 1/3
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| msyamp
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[left]oh ya i missed penetrance. 66/2 that is 33% o 1/3[/left]
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| gogetit
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y is it 2/3 chance for the child??
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| drk1980
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Coz its a two out of three chance that you will hv a live born affected, ie. an affected heterozygote.
Draw a punnetts square for urself(for better understanding) for an autosomal dominant disorder, with the father and mother both affected. They are both Aa, since both are affected.
dont bother abt AA since they die in utero. So for one birth you are now left with three possiblities for a live born. Out of the three live borns you have two chances to get an affected heterozygote(Aa). So thats why 2/3. ws tht understandable???
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| msyamp
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YES DRK YOU GOT IT.
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| gogetit
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thanks drk1980, i forgot that AA die in utero... thanks
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