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AP Biology 1.2 Evolution Drives the Diversity and Unity of Life 459 Views


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AP® Biology: Evolution Drives the Diversity and Unity of Life Drill 1, Problem 2. What was likely the first genetic material?

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Transcript

00:03

Here's your shmoop du jour, brought to you by gene material.

00:07

Denim, actually.

00:09

The first genetic material was likely... what?

00:12

And here are the potential answers...

00:19

Ok, so to determine which of the answer choices was the "first" genetic material, let's look

00:24

at the molecules in our answer choices...

00:26

DNA, RNA, proteins, an RNA-DNA hybrid molecule?

00:35

Well, we know the hybrid probably cuts down on fuel emissions... but we're not really

00:39

concerned with how "green" it is...

00:41

The theory about how life evolved on earth tells us that the first molecules were self-sufficient

00:47

because the earth wasn't "made" for us organisms...

00:51

and that they were relatively simple because there was nothing else to rely on at first.

00:55

Then as successful adaptations were developed due to the changing environment, these molecules

00:59

grew more and more complex.

01:01

It's how evolution works.

01:03

So the "first molecule" we want to find is the one that's the most self-sufficient and simple.

01:09

RNA stands for Ribonucleic acid.

01:15

It serves several functions in creating proteins for living cells...

01:19

It can act as a messenger to carry copies of genetic material...

01:23

...transfer amino acids to make proteins, and even self-replicate.

01:28

We'd say that's pretty self-sufficient.

01:30

We've also heard all about DNA when watching CSI...

01:34

and how it carries all of our genetic material...

01:37

and how we should never leave our DNA anywhere if we want to get away with some horrific crime.

01:43

DNA is a molecule that stands for Deoxy-ribonucleic acid....

01:47

which basically differentiates itself from RNA by having a different sugar base...

01:52

Deoxyribose instead of ribose.

01:55

Hence the difference between the D and R.

01:58

But as a piece of genetic material, it only contains the genetic blueprint.

02:02

Unlike RNA, it can't self-replicate or create proteins without RNA. So... not too self-sufficient.

02:11

Think about C. Proteins?

02:12

Well they're needed to interpret genetic information, but they're also the

02:16

product of the transformation from DNA to RNA.

02:20

So they can't be the first.

02:21

Finally, an RNA-DNA hybrid molecule would be nice as the first piece of genetic material...

02:27

but based on what we know about RNA, RNA doesn't really need DNA to function on its own.

02:34

RNA by itself is simpler...

02:36

So RNA is our first genetic material.

02:39

Answer's B.

02:40

Did you fill in that bubble all by yourself?

02:43

NOW who's self-sufficient?

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