[生物] 想請問一題普生

作者: yangboxx (鳥)   2015-07-31 13:38:36
14. John and Mary are planning to start a family. John was married once
before, and he and his first wife had a child with cystic
fibrosis. The brother of his current wife, Mary, died of cystic fibrosis.
What is the probability that John and Mary will have a
baby with cystic fibrosis? (Neither John, Mary, nor their parents have cystic
fibrosis.)
A) 1/4 B) 1/6 C) 1/8 D) 1/12 E) 1/16
答案是B
我的想法是
John是Tt,Mary是TT或Tt,所以不是1/2×1/4=1/8嗎!?
先謝謝各位大大~~
作者: BiGiLa (逼機啦)   2015-07-31 14:17:00
Mary TT/Tt機率並不是一半一半喔 TT1/3 Tt2/31/2 X( 2/3 X 1/2 ) = 1/6
作者: yangboxx (鳥)   2015-07-31 14:26:00
對喔!!謝謝大大~~

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