问题 单项选择题

用基因工程技术可使大肠杆菌合成人的蛋白质。下列叙述错误的是()

A.常用相同的限制性内切酶处理目的基因和质粒

B.载体上的抗性基因有利于筛选含重组DNA的细胞和促进目的基因的表达

C.可用含抗生素的培养基检测大肠杆菌中是否导入了重组质粒

D.导入大肠杆菌的目的基因不一定能成功表达

答案

参考答案:B

解析:常用相同的限制性内切酶处理目的基因和质粒,获得相同黏性末端。便于DNA连接酶连接,故A正确。载体上的抗性基因有利于筛选含重组DNA的细胞,不能促进目的基因的表达,启动子才是,故B错。重组质粒含有抗性基因,因此可用含抗生素的培养基检测大肠杆菌中是否导入了重组质粒,故C正确。导入大肠杆菌的目的基因不一定能成功表达,需要进检测盒鉴定,故D正确。考点:本题考查基因工程操作步骤相关知识,意在考查考生能理解所学知识的要点,把握知识间的内在联系能力。

单项选择题

Charles Darwin wed his cousin Emma and spawned 10 children, including four brilliant scientists. Albert Einstein’s second wife Elsa was his first cousin. Queen Victoria said “I do” to hers. So have millions worldwide. In parts of Saudi Arabia, 39% of all marriages are between first cousins.

In the U. S., though, the practice bears a stigma of inbreeding just this side of incest. The taboo is not only social hut legislative; 24 states ban the marriage of first cousins: five others allow it only if the couple is unable to bear children. A major reason for this ban is the belief that kids of first cousins are tragically susceptible to serious congenital illnesses.

That view may have to change. A comprehensive study published recently in the Journal of Genetic Counseling indicates such children run an only slightly higher risk of significant genetic disorders like congenital heart defects — about two percentage points above the average 3% to 4%. Says the study’s lead author, Robin Bennett, president-elect of the National Society of Genetic Counselors, which funded the study: “Aside from a thorough medical family history, there is no need to offer any genetic testing on the basis of consanguinity alone”.

Publication of the study will do more than tweak public awareness; it will enlighten doctors who have urged cousin couples not to have children. “Just this week,” says Bennett, “I saw a 23-year-old woman who had had a tubal ligation because her parents were cousins and her doctor told her she shouldn’t have children.”

The American proscription against cousin marriages grew in the 19th century as wilderness settlers tried to distinguish themselves from the “savage” Indians, says Martin, author of the book Forbidden Relatives: The American Myth of Cousin Marriage. “The truth is that Europeans were marrying their cousins and Native Americans were not.”

And doesn’t God have stern words on the subject Christie Smith, 37, a Nevada writer, says she felt guilty when she fell in love with her first cousin’s son Mark. “I was trying so hard to convince myself not to have these feelings,” she recalls, “that I went to the Bible looking for confirmation that it was wrong. And what I found was the exact opposite: support for cousin marriages.” The patriarch Jacob married two of his first cousins, Rachel and Leah. Smith married Mark in 1999.

The medical ban is lifted; the social stain may take longer to disappear.

Why did Christie Smith resort to the Bible()

A. Because God has stern words on cousin marriages

B. Because the Bible supports cousin marriages

C. Because she felt guilty falling in love with her cousin’s son

D. Because she wanted to know God’s words on cousin marriages

单项选择题