[00:00.00]Narrator: Listen to part of a conversation between two students. [00:03.83]The woman is helping the man review for a biology examination.
[00:08.04]Male Student: OK, so ... what do you think we should go over next?
[00:11.87]Female Student: How about if we go over this stuff about how bacteria become resistant to antibiotics.
[00:16.59]Male Student: OK.
[00:17.08]Female Student: Um, but first of all, though, how many pages do we have left? [00:20.87]I told my roommate I’d meet her at the library at seven o’clock.
[00:24.02]Male Student: Ummm ... There's only a few pages left. [00:27.44]We should be finished in a few minutes.
[00:29.27]Female Student: OK. So, ummm ...
[00:31.92]Male Student: About how bacteria become resistant to antibiotics.
[00:35.83]Female Student: Oh yeah, OK. So you know that some bacteria cells are able to resist the drugs we use against them, and that’s because they have these special genes that, like, protect them from the drugs.
[00:46.04]Male Student: Right. If I remember correctly, I think the genes, like ... weaken the antibiotics, or, like ... stop the antibiotics from getting into the bacteria cell, something like that?
[00:57.50]Female Student: Exactly. So when bacteria have these genes, it's very difficult for the antibiotics to kill the bacteria.
[01:04.28]Male Student: Right.
[01:05.13]Female Student: So do you remember what those genes are called?
[01:07.32]Male Student: Umm…
[01:08.43]Female Student: Resistance genes.
[01:09.85]Male Student: Resistance genes. Right. Resistance genes. OK.
[01:13.32]Female Student: And that makes sense, right? [01:14.46]Because they help the bacteria resist the antibiotics.
[01:17.52]Male Student: Yeah, that makes sense. OK.
[01:19.24]Female Student: OK. But the question is: how do bacteria get the resistance genes?
[01:23.58]Male Student: How do they get the resistance genes? [01:25.72]They just inherit them from the parent cell, right?
[01:29.66]Female Student: OK, yeah, that's true. They can inherit them from the parent cell, but that's not what I’m talking about.
[01:34.74]Male Student: OK.
[01:35.01]Female Student: I’m talking about how they get resistance genes from other cells in their environment, you know, from the other cells around them.
[01:42.31]Male Student: Oh, I see what you mean. [01:43.61]Umm, is that that stuff about “hopping genes," or something like that?
[01:47.94]Female Student: Right. Although actually they’re called "jumping genes,” not "hopping genes.”
[01:51.48]Male Student: Oh, OK. Jumping genes.
[01:53.35]Female Student: Yeah, but they have another name, too, that I can’t think of. [01:56.54]Umm ... let me see if I can find it here in the book ...
[01:59.44]Male Student: I think it’s probably on…
[02:01.49]Female Student: Oh, OK, here it is. [02:02.64]Transposons. That’s what they’re called.
[02:05.75]Male Student: Let me see. [02:07.39]OK. Trans …po ... sons …trans... posons. So "transposon" is another name for a jumping gene?
[02:15.66]Female Student: Right. And these transposons are, you know, like, little bits of DNA that are able to move from one cell to another. [02:22.83]That’s why they’re called "jumping genes." [02:24.89]They kind of, you know, “jump” from one cell to another.
[02:28.36]Male Student: OK.
[02:29.60]Female Student: And these transposons are how resistance genes are able to get from one bacteria cell to another bacteria cell. [02:36.42]What happens is that a resistance gene from one cell attaches itself to a transposon and then, when the transposon jumps to another cell...
[02:45.37]Male Student: The other cell gets the resistance gene and...
[02:48.06]Female Student: Right.
[02:48.54]Male Student: That's how it becomes resistant to antibiotics.
[02:51.03]Female Student: Right.
[02:51.44]Male Student: Wow. That's really cool. [02:52.81]So that's how it happens.
[02:54.03]Female Student: That’s how it happens.
托福14天冲刺微信战团