题干

某致病基因h位于X染色体上,该基因和正常基因H中的某一特定序列经BclⅠ酶切后,可产生大小不同的片段(如图一,bp表示碱基对),据此可进行基因诊断。图二为某家庭该病的遗传系谱。下列叙述错误的是(  )

A:h基因特定序列中BclⅠ酶切位点的消失是基因突变的结果

B:Ⅱ-1的基因诊断中只出现142bp片段,其致病基因来自母亲

C:Ⅱ-2的基因诊断中出现142bp、99bp和43bp三个片段,其基因型为XHXh

D:Ⅱ-3的丈夫表现型正常,其儿子的基因诊断中出现142bp片段的概率为1/2

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D

同类题5

阅读下面材料, 从每题所给的A, B, C, D四个选项中选出最佳选项。

C

    Life is full of surprises and you never know how things will turn out. Sir John Gurdon. Is a good example of this. As a boy, he was told he was hopeless at science and finished bottom of his class. Now, aged 79, the very same Gurdon shared the 2012 Nobel Prize in Medicine with Japanese stem cell (干细胞) researcher Shinya Yamanaka.

    Like so many scientists, Gurdon shows us where the power of curiosity and perseverance (坚持) can lead.

    At the age of 15 in 1948, Gurdon ranked last out of the 250 boys at his high school in biology and every other science subject. Gurdon's high school science teacher even said that his dream of becoming a scientist was quite "ridiculous".

    In spite of his teacher's criticisms, Gurdon followed his curiosity and kept working hard. He went to the laboratory earlier and left later than anyone else. He experienced thousands of failures.

    "I believe that we will, in the end, understand everything about how cells actually work." Gurdon said.

    In 1962, Gurdon took a sell from an adult frog and moved its genetic (基因的) information i nto an egg cell. The egg cell then grown into a clone of the adult frog. This technique later helped to create Dolly the sheep in 1996, the first cloned mammal in the world.

    In 2006, Gurdon's work was developed by Yamanaka to show that a sample (样本) of a person's skin can be used to create stem cells. Using the technique, doctors can repair a patient's heart after a heart attack.

    "Luck prefers the prepared mind." Gurdon told the Nobel Prize organization. "Ninety percent of the time things don't work, but when they do, you have to catch the chance."