问题 单项选择题

通过特殊方法,科学家将小鼠和人已分化的体细胞成功地转变成了类胚胎干细胞。有关分化的体细胞和类胚胎干细胞的描述,正确的是()

A.类胚胎干细胞能够分化成多种细胞

B.分化的体细胞丢失了某些基因

C.二者功能有差异,但形态没有差异

D.二者基因组相同,且表达的基因相同

答案

参考答案:A

解析:A.类胚胎干细胞具有分裂和分化成多种组织细胞的能力;选A。B.分化的体细胞不会丢失基因,只是基因的选择性表达;B错误。C.二者形态和功能都有差异;C错误。 D.二者基因组相同,但表达的基因不同,在不同的细胞中产生不同的mRNA和蛋白质,才导致细胞分化;D错误。考点:细胞分化的概念和原因。点评:本题比较简单,意在考查学生的识记和理解能力。

阅读理解

As we enjoy the summer ocean waves along the beaches, we may think nervously about Steven Spielberg's Jaws and the great fear that sharks inspire in us. Yet we are happy to see global efforts to protect the declining number of sharks. The world has realized that we need the species, like sharks, to keep a balanced ecosystem.

Sharks, in particular, are “in” these days. Thanks to good public policy and famous stars such as Jackie Chan and Ang Lee, killing sharks for fin soup is no longer cool.

The demand for shark fins has been rising for decades, threatening sharks with extinction(灭绝)—up to 100 million sharks are killed each year just for their fins. But we have started to reverse the trend, particularly in many areas of the United States and overseas where restaurants once proudly provided delicious shark fins on the menu.

In California, a ban on the sale and possession of shark fin soup has gone into effect this year through the efforts of Wild Aid and other organizations.

Overseas marketing and public efforts featuring posters on public transportation systems and TV ads have been underway for the past few years. These efforts all show signs of success, on both the supply side and the demand side of trade in shark fins.

Actually, stopping the killing of sharks is part of a broader movement to stop the killing of wild animals and the buying and selling of wildlife products. These products come from hunting elephants, tigers and rhinos, besides killing marine life.

Whether it is shark fin soup or ivory piano keys, killing animals is big business. The hunting of elephants in search of ivory tusks for luxury(奢侈的)goods has become a full­scale war. The decrease of African elephant populations is alarming. Together with international partners, the United States is leading the worldwide effort to reduce demand for high­end products that rely on killing animals.

小题1:The underlined word “reverse” in Paragraph 3 probably means ________.

A.show

B.keep

C.follow

D.change小题2:From the passage, we know ________.

A.Jackie Chan and Ang Lee make fin soup popular

B.a lot of wild animals have been killed for products

C.Steven Spielberg's Jaws inspires us to protect sharks

D.the number of African elephants has been increased小题3:.What can we infer from the passage?

A.More animals for high­end products will be saved.

B.People have kicked the habit of having shark fin soup.

C.Shark fins will not be available any more in restaurants.

D.Global efforts have succeeded in stopping killing wild animals.

判断题