问题 单项选择题

人体甲状腺滤泡上皮细胞具有很强的摄碘能力。临床上常用小剂量的放射性同位素131I治疗某些甲状腺疾病,但大剂量的131I对人体会产生有害影响。积聚在细胞内的131I可能直接()

A.插入DNA分子引起插入点后的碱基引起基因突变

B.替换DNA分子中的某一碱基引起基因突变

C.造成染色体断裂、缺失或易位等染色体结构变异

D.诱发甲状腺滤泡上皮细胞基因突变并遗传给下一代

答案

参考答案:C

解析:

DNA分子的元素组成中不含I元素,因此不能直接插入DNA分子或替换DNA分子中的某一碱基而引起基因突变,AB错误;放射性同位素131I能导致染色体结构变异,C正确;甲状腺滤泡上皮细胞是成熟的体细胞,不再进行细胞增殖,不会引起基因突变,并且突变后也不会遗传给后代,D错误。

考点:本题考查基因突变的特征和原因等相关知识,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。

阅读理解

第三部分:阅读理解(共20小题;每小题2分,满分40分)

阅读下列短文,扶每小题所给的四个选项(A、B、C和D)中,选出最佳选项,并在答题卡上将该项涂黑。

A

Be sure to book a table if the restaurant you choose is all expensive or a popular one.You will feel embarrassed to show up without booking and having to wait for a table, leaving very bad impression on your friend,especially your girl friend.Also,be sure to check to see if you need to be properly dressed and tell your fi4end ahead of time what to wear.

When your food arrives,proper dining manners make you eat at a right pace so that you have time to talk.A good measure of how fast you should eat is to count 10 seconds between each mouthful and it’s bad manners if you eat too fast and then spend the rest of the time watching your friend eat.

Don’t make noise when having soup and chewing,or chew with your mouth open.

Your napkin(餐巾)should be placed on your lap at ail times.Don’t put it in any other place;It you have to get up,place it nearly on your seat.

When eating,put your fork straight in your mouth.Don’t place your fork in the side of your mouth as it increases the chances of dropping your food,which could be very embarrassing.If you get food stuck in your mouth,don’t pick it out with your fingers or fork at the table.Excuse yourself and go to the restroom and get it out with a toothpick.

When dining,keep your eyes on your friend at all times and try to smile between mouthfuls. Some-times,you should make an effort to show some interest and ask questions like,“How do you like the beef?”If she needs, you are the one who is supposed to flag down the waiter fly a gentle wave of the hand until someone notices you.

56.If you want to eat in a popular restaurant,the author of the passage suggests that     .

A.you book a table beforehand

B.you book a table beforehand and check to be properly dressed

C.you go with a friend

D.you just show up any time you want

57.Good eating manners do NOT include          

A.eating at a proper pace

B.making sounds to show how much you enjoy food

C.showing some interest to your friend when dining

D.placing a napkin on your lap

58.We can infer from the passage for sure that           

A.the writer of the passage favors those dinning manners.

B.the writer of the passage is not a Chinese

C.toothpick is available in the restroom

D.toothpick is not to be found on a dinner table

59.The passage is mainly about          

A.dining manners                        B.an expensive restaurant

C.what to dress                        D.what to eat

单项选择题 案例分析题