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00:16

Okay, we're back with Shmoop Biology, and we're talking about transcription and RNA processing with Dr. Ruth.

00:23

So what are some similarities and differences between transcription and replication?

00:32

They both start with a DNA template.

00:36

They both involve a polymerase, so either DNA polymerase or RNA polymerase.

00:41

They both form new molecules that are composed of nucleotides.

00:46

So those are some of the similarities.

00:48

Differences? I think the main ones... One is that DNA replication happens over the whole genome, right? Like, all the DNA needs to be replicated when a cell divides.

00:55

Whereas only certain genes get turned on and transcribed at certain times.

00:59

So for transcription, the polymerase really needs to know where to start and where to stop.

01:04

For replication, it's kind of just...do the whole thing.

01:07

So that's really interesting. So this is, in the 23 chromosomes, it's gonna hop, and there's some that are just not lit up when it's transcribing?

01:15

Yeah. There are tons of genes on each of our chromosomes. So there's probably a few on each chromosome at any given time.

01:20

But, you know, if a cell is dividing, a certain set of genes will be turned on.

01:25

If a cell is just kind of sitting there, then it's gonna be a different set of genes.

01:28

And it just skips over it, like you're in the express, not the local train.

01:35

Another five-dollar word: what is a poly-A tail?

01:40

So that's another important difference between transcription and DNA replication.

01:44

RNA gets processed after it's made. So you go through the process of transcription, and you end up with an RNA molecule that isn't really mature...

01:50

You need to get some changes to it. And one of those changes is you have to add on a tail to the end of it.

01:55

It's a bunch of A nucleotides.

01:58

So these are just placeholders so that everything matches up sequentially?

02:02

It's basically added to the end. So it doesn't really need to match up, but there's just a sequence at the end.

02:05

To be honest with you, I have no idea what those do... sorry!

02:07

Ha, okay, then it can't be that important. PhD here...don't worry about it.

02:12

And that's it for Lesson 7. We're gonna move on to the next one.

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