下列有关基因的说法不正确的是（） A.基因都是通过控制酶的合成_爱下问搜题

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问题单项选择题

下列有关基因的说法不正确的是（）

A.基因都是通过控制酶的合成控制生物性状

B.基因是有遗传效应的DNA或RNA片段

C.基因以一定的次序排列在染色体上

D.基因是生物遗传的基本功能单位

答案

参考答案：A

解析：基因可通过控制酶的合成控制生物性状，还能通过控制蛋白质的结构直接控制生物体的性状，A错误；基因是有遗传效应的DNA片段，对于遗传物质是RNA的病毒是遗传效应的RNA片段，B正确；基因在染色体上呈线性排列，C正确；基因是具有遗传效应的DNA片段，是决定生物性状的遗传物质的基本单位，D正确。

考点：本题考查基因的概念等相关知识，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的能力。

选择题

可以肯定溶液中大量存在CO₃^2-的理由是[ ]

A．加入AgNO₃溶液有白色沉淀生成

B．加入酸有无色气体产生

C．加入CaCl₂溶液时有白色沉淀产生，再加稀盐酸沉淀溶解，产生可使澄清石灰水变浑浊的无色无味的气体

D．加入Ba(OH)₂溶液有白色沉淀产生，再加稀盐酸，产生可使澄清石灰水变浑浊的无色无味的气体

完形填空

One day my 5-year-old daughter, Mini, ran to the window crying: “A Cabuliwallah! A Cabuliwallah（从喀布尔来的水果商贩）!” In the street below was a Cbuliwallah,1 slowly along. Mini called him loudly but when he looked at her，she ran away, 2 . Shortly after this, the two became friends. They started to 3 together, laughing and talking. Mini’s new friend would give her sweets and nuts, 4 the little money he had on her.The Cabuliwallah, called Rahmum, would joke: “Well, little one, when are you going to the father-in-law’s house?” Mini did not understand this and was 5 .
One morning, I heard noise in the street, and saw Rahmum being led 6 by the police. There were bloodstains on his clothes. I gathered that a neighbor had 7 Rahmum money for a shawl (披肩)but had falsely 8 having bought it, and that in the course of the quarrel Rahmum had struck him. On a charge of murderous attack, Rahmum was 9 to jail.
Time passed, and he was not remembered. Mini grew up and we were making 10 for her wedding. I was sitting in my study when someone entered. It was Rahmum, 11 from prison.12 recognizable now, he asked to see Mini and said that all those years ago she had 13 him of his own daughter in Kabul. It was his belief that Mini was still the same. He had 14 her running to him calling “Cabuliwallah!”. He had imagined that they would laugh and talk together. In fact, he had brought her,15 in paper, a few nuts and grapes. The two were 16 but Mini had grown up. She now understood the meaning of the word “father-in-law,” and when he made this joke once more she was 17 in the face at the question. He could not revive(还原) their old friendship.
When Rahmum left, I gave him a bank note, saying:“Go back to your own daughter, and 18 the happiness of your meeting bring good fortune to my child! ”
Having made this present, I had to 19 the electric lights and the military band I had 20 for the wedding and the ladies in the house were disappointed. But to me the wedding feast was all the brighter for the thought that in a distant land a long-lost father met again with his child.

D．disappointed

A．appointments

D．arrangements

A．Immediately