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IELTS Preparation Series 1, Episode 14: Junk DNA

September 3, 2016

 

(Bấm vào đây để xem/nghe bài kế tiếp)

 

Xem lời thoại bên dưới:

 

0:00

Hello. I'm Margot Politis. Welcome to Study English, IELTS preparation.

0:19

Today we're going to look at conditional sentences. They're sentences that use 'if'.

0:26

If you listen carefully, you'll be able to hear Dr Malcolm Simons talking about junk

0:31

DNA, the parts of DNA that people used to think were just rubbish. Listen to the different

0:37

types of sentences he uses.

0:40

Under Darwinistic notions, you would think that junk would drop off under the theory

0:48

of natural selection, just like species drop off if they hit ecological niches, which is

0:53

incompatible with survival. If they can adapt to those niches, then those that can, survive,

1:02

and those that can't, die, is the notion. If you apply that to the DNA sequence, then

1:09

the coding region genes, which survive, have a function, and by the way the non-coding

1:15

sequences have survived as well. So the proposition would have to be that if they're there, they've

1:22

got a function.

1:23

In listening to Dr Simons, you can hear that he uses a variety of sentences. This makes

1:29

for much more interesting language. You should practice using sentences of different lengths

1:34

and types, especially complex sentences.

1:38

Today we're going to look at one of the ways you can create complex sentences using an

1:43

'if clause'.

1:45

An 'if clause' is a phrase that gives a condition that's necessary for something else to happen.

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They're often called conditional clauses.

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If means when, provided that, or on condition that.

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There are a few basic patterns for the 'if clause'.

2:05

Listen to this:

2:07

If they can adapt to those niches, then those that can, survive, and those that can't, die.

2:15

So the proposition would have to be that if they're there, they've got a function.

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If they can adapt, then those that can survive.

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The pattern here is: if + simple present tense verb, then ….

2:34

Then introduces a clause describing the consequences.

2:40

Look at the second example in the extract.

2:43

If they are there, they have got a function.

2:47

Notice that the then is left out in this example. Then is optional.

2:54

He could have said if they are there, then they have a function.

3:00

Let's look at some more.

3:03

If you have a university education, then you have more opportunities.

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But the then is optional - you can leave it out.

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If you have a university education, you have more opportunities.

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Notice that this pattern can be reversed.

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You have more opportunities if you have a university education.

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We never include then when the pattern is reversed like this.

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Let's try with the example from the story.

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If they're there, they have a function.

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They have got a function, if they're there.

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OK, now here's the second pattern for 'if' sentences.

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This is for when the suggestion is less definite, or less likely.

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If you had a university education, then you would have more opportunities.

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The pattern here is: if + past tense, then + would + verb.

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If you had a university education, then you would have more opportunities.

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We use this pattern when we are talking about the future, and about something that may not

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be as likely to happen.

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Compare these 2 patterns.

4:28

If you study hard, then you will pass your test.

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If you studied hard, then you would pass your test.

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In the first example, it's a bit like making a useful suggestion.

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The second sentence is less definite, and less polite. It suggests that the person doesn't

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study hard now.

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So that's 2 ways of making the conditional tense - how to say that one thing will happen,

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or might happen, if something else happens. There are other forms of the conditional tense

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too.

5:04

If you learn them, then your English will improve!

5:07

OK, now we're going to look at ways of making opposites by using prefixes.

5:18

Listen to Dr Simons again.

5:21

Under Darwinistic notions, you would think that junk would drop off under the theory

5:28

of natural selection, just like species drop off if they hit ecological niches, which is

5:34

incompatible with survival. If they can adapt to those niches, then those that can, survive,

5:43

and those that can't, die, is the notion.

5:47

If you apply that to the DNA sequence, then the coding region genes, which survive, have

5:53

a function and by the way the non-coding sequences have survived as well.

5:58

In the passage we heard the words survive and die. They have opposite meanings.

6:05

'To survive' means to keep on living and 'to die' means to stop living. We call words with

6:12

opposite meanings, opposites.

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Sometimes opposites are formed from the same word stem using prefixes. Two of the prefixes

6:22

he uses are 'in' and 'non'.

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Listen:

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And by the way the non-coding sequences have survived as well.

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He calls the junk DNA the non-coding sequences.

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Non-coding means not coding. Notice that we use a hyphen with the non- prefix.

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Non- usually forms adjectives.

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It means 'not in the group of', so we have non-European, non-Aboriginal or non-government.

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Non- can also just means not, giving a negative sense to a word - non-fiction, non-smoking

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and non-stick.

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The prefix 'in' is used with adjectives as well. It also makes opposites, and means 'not'.

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It forms words like: insignificant, not significant; inexpensive, not expensive; intolerant, not

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tolerant.

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Another common opposite prefix is un-.

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We can have unfair, unattractive, unusual, unnatural.

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But un- can also be used with verbs. It means that an action is reversed.

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So we have undo, undress or unbend.

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There aren't many rules about what sorts of words take these prefixes. You'll have to

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learn most opposites one by one.

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A good way to do this is to try to find out the opposite every time you come across a

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new word.

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Finally for today, let's have a look at how you can form adjectives from people's names.

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Under Darwinistic notions, you would think that junk would drop off under the theory

8:16

of natural selection.

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He says under Darwinistic notions.

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Darwinistic here is an adjective, but it's got a capital letter - do you know why?

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Well, that's because It comes from the name 'Darwin' - referring to Charles Darwin, who

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developed the theory of natural selection.

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But it's got 2 suffixes: -ist and -ic.

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The -ic suffix forms adjectives that mean belonging to, or like. So 'Darwinistic' means

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like a Darwinist.

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But a 'Darwinist'?

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Well the suffix -ist forms adjectives too, but it forms an adjective that describes a

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type of person with a certain set of beliefs.

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When -ist is added to people's names, it means someone who follows that person, or who believes

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in what they wrote or said.

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So we can have a Darwinist, someone who believes in Darwin's theories, or a Marxist, someone

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who follows the writings of Marx, or a Buddhist, someone who follows the teachings of the Buddha.

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Well, we're out of time for today. Remember to watch out for those opposites, and try

9:31

using 'if' clauses.

9:33

See you next time. Bye Bye.

 

 

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