题干

下列说法错误的是(   )

A:三倍体无子西瓜的性状可以遗传,但它不是一个新物种。用一定浓度的生长素处理未授粉的四倍体西瓜幼苗,可获无子西瓜,这种性状不可遗传

B:一块水稻田中偶尔发现一株矮秆水稻,它连续自交后代都是矮秆,这种变异可能源自于体细胞或生殖细胞的基因突变

C:染色体结构变异和基因突变的实质都是染色体上的DNA中碱基对排列顺序的改变

D:一个基因型为AaBbCC的植物(三对基因可自由组合),用其花粉离体培养获得n株幼苗,其中aabbCC的个体的比例为0

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答案(点此获取答案解析)

C

同类题4

阅读理解

B

    Many blind people use guide dogs to help them get safety from place to place and to warn them of danger. But what can blind people do if they are allergic(过敏的)to dogs or just don't like them? For some people, the answer is provided by the Guide Horse Foundation.

    Janet and Don Burleson founded the organization in 1999. They began training miniature horses to help guide blind people. Miniature horses look just like regular horses, only much smaller. They are generally less than 34 inches tall.

    Cuddles was the foundation's first guide horse in full service(服务). She became 45-year-old Dan Shaw's helper. Shaw has an eye disease and his sight is very poor. One night, while filling out a form to get a guide dog, Shaw heard a news story on TV about people training horses to guide the blind. Shaw loves horses and wanted a guide animal that would live a long time. He applied(申请), and a year later, Cuddles and Shaw began training as a team.

    On a trip to New York, Cuddles helped Shaw safely tour Times Square, a very busy part of the city at night. The next day, Cuddles calmly rode the elevator with Shaw to the crowded top of the Empire State Building, a famous tall building. Cuddles even guided Shaw on the boat ride to the Statue of Liberty(自由女神像), and traveled on the subway system.

Shaw says that he is very lucky to have Cuddles. He believes that Cuddles has changed his life for the better by giving him more freedom.