题干

某种鼠中,黄鼠基因Y对灰鼠基因y为显性,短尾基因T对长尾基因t为显性。且基因Y或t纯合时都能使胚胎致死,这两对基因是独立遗传的,现有两只双杂合的黄色短尾鼠交配,理论上所生的子代表现型比例为(  )

A:4∶2∶2∶1

B:2∶1

C:9∶3∶3∶1

D:1∶1∶1∶1

上一题 下一题 0.0难度 选择题 更新时间:2013-12-17 08:43:36

答案(点此获取答案解析)

B

同类题5

阅读理解

    First published in 2001, the book Life of Pi written by Canadian author Yann Martel won the Man Booker Prize and an Asian American Prize for Literature. It is the story of a young boy named Pi who spends 227 days at sea with a small group of animals after disaster strikes their ship and is an account of his journey of survival and hardship.

    Piscine “Pi” Molitor Patel, on whom Life of Pi is based, is a young boy living in Pondicherry, India, where his father owns a zoo. The story starts when Patel's family decide to move to Canada, along with their zoo animals for their new home.

    However, because of the bad weather, the ship sinks. Pi along with an orangutan (猩猩), an injured zebra, a hyena (鬣狗) and a Bengal tiger named Richard Parker are the only survivors who take shelter in a small lifeboat. Both the injured zebra and the orangutan are soon killed and eaten by the hyena. The tiger in turn kills and eats the hyena, leaving just the two of them alone on the boat now.

    In an effort to avoid being eaten by Richard Parker, Pi acts himself as the head of the group and remains safe from harm. Since he does not want the tiger to die for fear of going mad by being alone on the boat, he fishes and feeds the two of them in order to stay alive.

    The life of Pi then enters its third stage when their lifeboat washes up on the shores of Mexico and the tiger escapes into a nearby forest leaving Pi alone. After the Mexicans refuse to believe Pi's story, he changes his tale by replacing the animals with his mother, a cook and a sailor and asks the Mexicans which one they prefer. They prefer hearing the first story though they do not believe a word of it.

    In my view, Life of Pi is a must read book for all those who love reading.