6. What does the professor mainly discuss?（主旨题）

　　A. How genes control human development.

　　B. Why various types of human cells divide at different rates.

　　C. How human chromosomes differ from one another.

　　D. Why most human cells cannot keep dividing successfully.

　　7. The professor discusses research about the percentage of a chromosome’s DNA that contains genetic information. How did she feel about this research?（态度题）

　　A. She doubted its accuracy.

　　B. She was surprised by its conclusion.

　　C. She was concerned about its implications.

　　D. She thought it was unnecessary.

　　8. What does the professor say about the DNA in a telomere?（细节加推断题，易错点）

　　A. It causes a cell to begin dividing.

　　B. It separates one gene from another.

　　C. It is genetically meaningless.

　　D. It has no function.

　　9. Why does the professor mention shoelaces?（修辞目的题）

　　A. To point out that chromosomes are arranged in pairs.

　　B. To describe the coiled shape of a chromosome.

　　C. To illustrate how chromosomes are protected from damage.

　　D. To explain how chromosomes are joined before dividing.

　　10. What does the professor imply about the length of the telomeres on a cell’s chromosomes?（推断题）

　　A. Longer telomeres allow the cell to divide more times.

　　B. Longer telomeres contain more genetic information.

　　C. Shorter telomeres are wound into tighter coils.

　　D. Shorter telomeres are less likely to break.

　　11. According to the professor, how is the chemical telomerase related to the telomere?（细节题）

　　A. It resembles the telomere in structure.

　　B. It helps repair broken telomeres.

　　C. It is produced at the end of telomere.

　　D. It prevents telomeres from becoming too long.

　　生物类常见的逻辑结构：在课堂演讲中，教授常常会就某一生物现象或者生物特征进行讲解，并举出相应的例子进行证明，期间往往会有老师的自问自答和已经和学生之间的讨论。

　　本文的逻辑结构：背景引入式开头，以一个重要的observation开头，实验室里的细胞在分裂特定的次数之后会死亡------But转折之后引出今天的课堂的重点，所有细胞最终不会renew而是走向死亡-----人体细胞是怎么分裂的，引出染色体概念---人体有23对染色体46条DNA----meaningful genetic information20%和junk DNA占据的比例70%----JUNK DNA有其他的用途，如它的典型代表telomere以及特征-----telomere在细胞每次分裂之后会变短，这是它的一个缺点，使得染色体失去重要基因信息，失去功能，也是细胞最终会死亡的原因-----telomerase新概念的提出，关于telomerase的作用，telomerase 可以修复telomere------the use of telomerase的发展前景

　　一句话概括：Human cell division before they die------how it happens---why it happens

　　长难句跟读练习：

　　1 then may be we can explain a very important observation,that when we try to grow most human cells in libratory, they seem programmed to divide only a certain number of times before they die

　　2 You see that it sort of looks like, well actually it’s much more complex than this but it reminds us a couple of springs linked together to coil up(盘卷成) pieces of DNA. （将DNA类比成弹簧。）

　　3 Now a telomere is a highly repetitious and genetically meaningless sequence of DNA,what we were calling JUNK DNA. But it does have any important purpose;

　　4 it is sort of like the plastic tip on each end of shoe lace.It means not help you tie your shoe but that little plastic tip keeps the rest of the shoelace, the shoe string from unraveling into weak and useless threads.

　　5 Someday we may be able to take any cell and keep it alive functioning and reproducing itself essentially forever through the use of telomerase.