[Caitlin:] I see you found my tiara... [Felicia:] Well, I've been thinking about it,

and maybe you're not the only one with royal relatives.

Maybe there is noble blood flowing through these veins, too.

[Caitlin:] Well,

you won't know until you send in that sample

and have the ancestory test done. [Felicia:] I'm working on it.

I just can't seem to get my salivary glands to cooperate.

[Caitlin:] Would you like me to make you mad?

[Felicia:] Go for it.

[Caitlin:] Okay. Zombies are not real.

I hate zombies. Zombies are stupid.

[Felicia:] Ahhh, I'll show you! [Spits]

[Caitlin:] Well, this is all very exciting.

Seriously, what do you think the results will tell you about your ancestors?

[Felicia:] Well, that they're Romanian mostly...

Quite possibly a little bit of zombie, as well.

[Caitlin:] Well, that wouldn't surprise me,

but I'm pretty certain the undead isn't included in

the analysis.

[Felicia:] What?! What's even the point then? [Caitlin:] I thought you said you wanted to find

out if you were royalty. [Felicia:] Yeah, I was kind of hoping there was

a zombie queen in my family tree. [Caitlin:] Dead certain there ain't.

But you won't know anything until you send off the sample.

Then we can talk about all things ancestry-related,

this week on... [Both:] DNA Decoded!

[MUSIC]

[Caitlin:] Okay, so let's imagine that, just like Felicia,

you spit in a tube and you send it off for DNA analysis.

The company will analyze your spit and tell you about your family tree.

There are plenty of videos on YouTube where folks reveal their

DNA ancestry results.

You can check it out, if you don't believe me.

Not that I've ever binge-watched YouTube or anything!

[Felicia:] Celtic princess!

But you might be asking, why spit?

Why not take a blood sample or a cheek swab?

Getting a blood sample is pretty invasive, and who likes needles?

Plus, it would be dangerous, dumb, and impractical for people to take

their own blood samples at home. [Caitlin:] Next: cheek swab.

A cheek swab is what is called a dry method.

It's pretty non-invasive.

But you still have to stick something in your mouth to scrap off

the cells from the inside of your cheek.

Plus, the sample can be contaminated with mouth bacteria.

Yes, even those of us who floss have mouth bacteria.

[Felicia:] But spit -- that's the winner here.

Spitting in a tube is called the wet collection method for obvious reasons.

It's totally noninvasive because you spit into a tube.

You don't put the tube in your mouth, unless you didn't read the instructions.

[Caitlin:] You did read the instructions, right?

[Felicia:] Yeah.

Did you know your spit contains almost as many white blood cells as a blood sample?

It does!

When you close up the spit tube you get from the testing company,

a buffer is automatically added.

That chemical stabilizes your DNA

so we won't get damage, even if there are extreme changes in

temperature during shipping. [Caitlin:] Okay.

That's why you need to spit in a tube.

But what happens after you ship it off? [Felicia:] There are a handful

of genetic geneology tests out there.

And there are lots of different companies that offer variations on those tests.

We're not going to tell you which is the best, because that's up to you.

But we are going to talk about some of the ways that testing is done.

[Caitlin:] The first method is to look at

what's called your autosomal DNA.

That's the DNA that's in the 22 chromosomes that you inherited from

both of your parents. [Felicia:] Um, 23 chromosomes, Cait.

[Caitlin:] Yes, we have 23 chromosomes, but

the 23rd pair are the sex chromosomes.

That pair gets dealt with a little differently.

We'll talk about it in a minute...

Many researchers use autosomal DNA in their studies because it provides

a richer, more complicated picture of your genetic makeup.

Remember when we said that humans are over 99 percent genetically the same?

Well, comparing the less than one percent variation in our genes provides us with a lot of

information about what makes us, us.

We can now test and compare about 700 000 sites on these chromosomes.

This information can be used to determine family relationships -- second cousins

three times removed and that kind of thing -- as well as our ethnic heritage.

Autosomal testing can go back about seven generations or

210 years into your past. [Felicia:] The second method is to

just take a look at the X-chromosome in our sex chromosome pair.

You probably know that a male inherits an X-chromosome from his mother,

while a female inherits an X-chromosome from both her mother and her father.

Tracing your X-chromosome through the family lineage gives

broad information on your ancestral roots. [Caitlin:] The third method is to look at your

Y-chromosome -- if you have one.

This method allows males to trace their family back through male ancestors.

If you're a woman who wants to trace your paternal lineage and

you want to have this test done, you'll have to recruit a male relative

on your father's side who's willing to be tested.

The Y-chromosome is passed down from father to son,

basically unchanged through generations except for random mutations.

These random mutations are called markers.

They happen naturally and are usually harmless.

Once the markers have been identified, geneticists can go back in time and

trace them to the point at which they first occurred.

People who share the same mutation share a common ancestor

and belong to what is a haplogroup.

Scientists found a mutation of the Y-chromosome that spread very rapidly across

Asia about a thousand years ago.

Nearly 16 million men, almost 8 percent of the male population in the region,

have Y-chromosomes that are nearly identical.

What could cause this?

Well, the men are living in the same region as the former Mongol Empire.

The genetic evidence and the historical records that describe the Mongol invasion

suggests that 16 million men are descended from Genghis Khan

and his male relatives. [Felicia:] So far, we've talked about testing

the 23 chromosomes that are contained in a cell's nucleus.

However, did you know that you have more genes?

The mitochondrion is the only other place that stores genetic information

outside the nucleus.

And it's much easier to analyze than the DNA found in your chromosomes.

Typically, the mitochondrion contains an additional 37 genes that mostly encode for

the type of RNA that helps us build proteins.

You might remember we talked about the mitochondrion in passing in Week 1.

We called it the powerhouse of the cell because it produces the energy that

the cell needs to function.

The mitochondrion looks a bit like a kidney.

You also remember DNA plasmids, right?

DNA that's in a ring instead of a linear double helix.

Well, mitochondria have circular DNA plasmas in it.

[Caitlin:] This DNA is unique in the way it's inherited.

We usually think about DNA as half coming from your mother and

half from your father.

Well, mitochondrial DNA is an exception.

We inherit it only from our mother.

That's right --

no matter who you are, your mitochondrial DNA came from your mother.

So, we can use it to trace maternal lineages.

[Felicia:] Not only that, but

we can use mitochondrial DNA as a sort of molecular clock.

Mitochondrial DNA contains a region that changes rapidly.

We know that every so often a mutation will occur.

We can use this information to calculate how old DNA samples are.

Hey, we forgot about one final test.

The one that looks at the Z-chromosome! [Caitlin:] Ugh! Felicia, there is no Z-chromosome.

[Felicia:] Tell that to

my great, great-grandmother, the queen of the zombies.

So, quick recap.

We explained why spit is the best fluid for sending to genealogy DNA companies.

They can use the DNA in saliva to give you a better idea of where you're from

and what quirks you share with the folks in your family photographs.

We've talked about how we can use DNA to trace our heritage and lineage,

even back thousands of years and lots of generations.

That's true whether they're in 22 of our chromosomes, our sex chromosome,

or our mitochondria.

I'm hungry again. [Caitlin:] What do you feel like eating?

[Felicia:] Brain!

[Caitlin:] Ugh! You're such a goof!

Let's go get some cake.

[MUSIC]

Me and My Family Tree

DNA Decoded

Meet the Instructors