【正文】 TPO 12 – Listening Part Part 1 Script: TPO 12 Conversation1 Narrator Listen to a conversation between a student and a professor. Student So Professor Tibets, your notes said that you want to see me about my heavyweight paper. I have to say that grade wasn’t what I was expecting. I thought I’d done a pretty good job. Professor Oh, you did. But do you really want to settle for pretty good when you can do something very good? Student You think it can be very good? Professor Absolutely! Student Would that mean you’d…I could get a better grade? Professor Oh, sorry! It’s not for your grade. It39。s…I think you could learn a lot by revising it. Student You mean, rewrite the whole thing? I really swamped. There’re deadlines wherever I turn and… and I don’t really know how much time I could give it. Professor Well, it is a busy time, with spring break ing up next week. It’s your call. But I think with all a little extra effort, you could really turn this into a fine essay. Student No… yeah…I mean, after I read your ments, I...I can see how it tries to do too much. Professor Yeah. It’s just too ambitious for the scope of the assignment. Student So I should cut out the historical part? Professor Yes. I would just stick to the topic. Anything unrelated to the use of nature EMITRY has no place in the paper. All that tangential material just distracted from the main argument. Student Yeah, I never know how much to include. You know…where to draw the line? Professor Tell me about it! All writers struggled without one. But it’s something you can learn. That will bee more clear with practice. But I think if you just cut out the…emm… Student The stuff about history, but if I cut out those sections, won’t it be too short? Professor Well, better a short wellstructured paper than a long paper that poorly structured and wanders off topic. Student So all I have to do is to leave those sections? Professor Well, not so fast. After you cut out those sections, you’ll have to go back and revise the rest, to see how it all fits together. And of course, you’ll have to revise the introduction too, to accurately describe what you do in the body of the paper. But that shouldn’t be too difficult. Just remember to keep the discussion focused. Do you think you can get it to me by noon tomorrow? Student Wow…emm…I have so much…er…but I’ll try. Professor OK, good! Do try! But if you can’t, well, sure for after spring break, OK? TPO12 – Lecture 1 Narrator Listen to part of a lecture in a Biology Class. Professor As we learn more about the DNA in human cells and how it controls the growth and development of cells, then maybe 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. Now this differs with the type of cell. Some cells, like nerve cells, only divide seven to nine times in their total life. Others, like skin cells, will divide many, many more times. But finally the cells stop renewing themselves and they die. And in the cells of the human body itself, in the cells of every an, of almost every type of tissues in the body, the same thing will happen eventually. OK, you know that all of persons’ geic information is contained on very long pieces of DNA called Chromosomes. 46 of them are in the human cells that’s 23 pairs of these Chromosomes are of very lengths and sizes. Now if you look at this rough drawing of one of them, one Chromosome is about to divide into two. You see that it sort of looks like, well actually it’s much more plex than this but it reminds us a couple of springs linked together to coil up pieces of DNA. And if you stretch them out you will find they contain certain genes, certain sequences of DNA that help to determine how the cells of the body will develop. When researchers look really carefully at the DNA in Chromosomes though, they were amazed, we all were, to find that only a fraction of it, maybe 2030%, converts into meaningful geic information. It’s incredible。 at least it was to me. But if you took away all the DNA that codes for genes, you still have maybe 70% of the DNA left over. That’s the socalled JUNK DNA. Though the word junk is used sort of townies cheek. The assumption is that even these DNA doesn’t make up any of the genes it must serve some other purpose. Anyway, if we examine these ends of these coils of DNA, we will find a sequence of DNA at each end of every human Chromosome, called a telomere. Now a telomere is a highly repetitious and geically meaningless sequence of DNA, what we were calling JUNK DNA.