问题 实验题

孔雀鱼是一种常见的观赏鱼,其性别决定方式属于XY型,是非常好的遗传学实验材料。几十年前,德国的一位育种者在众多的孔雀鱼幼鱼中发现一条身体后半部为暗色的个体,并以此个体为基础培育出了“礼服”品种。用“礼服”品种的雌鱼作亲本(P)与其它品种的雄鱼杂交,所得子代(F1)个体中,雌雄鱼均表现“礼服”性状;将子代(F1)雌雄个体自由交配,所得子代(F2)个体中,雌鱼均表现“礼服”性状,雄鱼表现为1/2“礼服”性状、1/2无“礼服性状。请用“假说一演绎法”对“礼服”性状的遗传进行研究。

(1)发现问题:在研究中发现“礼服”性状的遗传与________相关联。

(2)作出假设:“礼服”为_______(显性或隐性)性状,控制该性状的基因位于______染色体上。

(3)演绎推理:题干F1中雌雄性个体的基因型分别是___________(分别用A、a表示显隐性基因),F2中雌鱼基因型是_________,雄鱼基因型是___________。

(4)实验检验:请你设计一个实验来验证假设(请用遗传图解加以说明)。

答案

(1)性别

(2)显性     X

(3)XAY、XAXa         XAXA和XAX      XAY和XaY

(4)

阅读理解

London police are well known in the world. Today there are policemen everywhere, but in 1700 there was no policeman in London at all. A few old men used to protect the city streets at night, and they were not paid very much.

About 300 years ago, London started to get bigger. The city was very dirty and many people were poor. There were so many thieves who stole money in the streets that people had to stay in their homes as much as possible.

In 1750, Henry Fielding started to pay a group of people to stop thieves. They were like policemen and were called “Bow Street Runners” because they worked near Bow Street.

Fifty years later, there were 120 Bow Street Runners, but London had become very big and needed more policemen. So, in 1829, the first London Police Force was started with 3,000 officers. Most of the men worked on foot, but a few rode horses. There was no policewoman in London until 1920.

Today, London police are quite well paid and only a few police officers still ride horses.

Perhaps the London Police Force’s greatest achievement (成就) is to meet changing  conditions and provide excellent police service (服务). The two main reasons for the Force’s development were the growth of population and the progress of science and technology.

小题1:London Police Force is famous in the world, because _________.

A.it provides excellent service

B.it has many policewomen

C.the police officers work on horses

D.it has a long history小题2:People in London didn’t want to go outdoors about 300 years ago because __________.

A.there were no policemen in the streets

B.the city was very dirty

C.they were poor

D.there were so many thieves in the streets小题3:London had 120 Bow Street Runners in the year of __________.

A.1700

B.1750

C.1800

D.1829小题4:Which of the following sentences is true according to the passage?

A few policeman protected the city streets at night in 1700.

B.The first London Police Force was founded in 1829.

C.London police were well paid in the past.

D.People could not see policewomen until 1900.

小题5:What is the best title for this passage?

A.London Police Force

B.Bow Street Runners

C.Why Are London Police Famous?

D.The History of the London Police

问答题