California has some really big trees.
Between the giant sequoias and the coast redwood,
if you want to see a big tree, this is where you come.
But their size isn't the only big thing about them.
Their genomes are also gigantic.
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The human genome is 3.2 billion bases long.
That's 3.2 billion As, Ts, Cs, and Gs
that make up the instructions for you and me.
And we each have two copies of our genome, one from our mom,
and one from our dad.
And when I say 3.2 billion, I think, OK, that's a big number.
But it's really hard to actually conceptualize just
how big of a number a billion is.
I wanted to do a demonstration of this.
So I thought, OK, I'm going to get 3.2 billion grains of rice.
Then that'll show people how big 3.2 billion is.
But when I did the math, 3.2 billion grains of rice
would weigh about 93,000 kilograms.
That's 205,000 pounds.
That's like 17 elephants' worth of rice.
And my apartment is not big enough for that.
So fine.
How about grains of sand?
Average grain of sand weighs around 0.0044 grams.
So that's around 14,000 kilograms,
still way too much sand.
So an average human head has around 100,000 hairs.
So that's like 32,000 people worth of hair.
That's just about all of the hair of all of my subscribers,
assuming that at least some of you are bald.
But that's still not a great metric.
So what about measuring in trees?
Well, you may have heard about the Team Trees collab, headed
by Mr. Beast and Mark Rober, which
aims to plant 20 million trees by raising money
through the Arbor Day Foundation.
This is an awesome goal.
And we'll talk a bit more about that later on in the video.
But if they plant 20 million trees,
they would have to do that 160 times to plant as many trees
as there are base pairs in just one copy of the human genome.
But what about a tree genome?
Well, the giant sequoia, its genome is 8 billion bases long.
It, like humans, is diploid, meaning
it has two copies of its genome, one from each parent tree.
But the coast redwood, the tallest tree
in the world, each copy of its genome
is 27 billion bases long.
And it's a hexaploid, meaning it has
six copies of its genome, three copies from each parent tree.
And that is so much DNA, and why?
Well, we should start by looking at what's in those genomes.
And that's exactly what the Redwood Genome
Project is doing.
Earlier this year, they published the first full genome
sequences from the coast redwood and the giant sequoia.
To sequence whole genomes, scientists
read the genome in small pieces and then assemble
all of those pieces back together like a giant puzzle.
And as you might imagine, the bigger the genome,
the harder this assembly process can be.
But the two genomes were made public earlier this year.
And they can now act as the reference for the broader
populations of trees.
One of the goals of the project is
to look at genetic diversity among the tree populations
by looking at lots of different trees.
So having a reference is a great way to start
and an important way for other scientists
to compare their own data back to that reference.
Now of course, this doesn't mean that the reference
is the "best" tree or the "correct" genome sequence.
It's just a solid starting point that lots
of different researchers can now compare their data back to.
But what I do think is pretty wild
is that these reference sequences
came from tree samples that were taken from trees that
were each over 2000 years old.
That's amazing, mind boggling.
Again, my brain struggles to truly comprehend
the span of 2000 years.
Now that we have a reference genome,
scientists can start to look at the genetic diversity of trees
in the forests for management.
Selective harvesting of trees can thin out some areas,
freeing up water and sunlight for the remaining trees
to grow.
And looking at their DNA can allow scientists
to make better decisions about which trees to cut
and which trees to leave.
Ensuring that there's lots of genetic diversity
in the remaining population can give the trees
the best possible chance to be able to adapt and evolve
as the environment around them changes
over the span of thousands of years.
Again, crazy.
So why do these big trees have huge genomes?
It's not just a body-size thing.
In fact, the largest genome sequence to date is
the axolotl, or "ah-sho-lot," genome.
And those are pretty small organisms.
Often, genomes grow because of duplication events
where, just as it sounds, the entire genome
is duplicated in the organism.
The coast redwood has evidence of these kinds
of duplications in its past, leading to its hexaploidy.
Genomes can also grow because of the accumulation
of repetitive regions of DNA.
And the specifics of the how are a story for another time.
But the best hypothesis about these trees
right now is that these large genomes
can help enhance genome dynamicism, allowing organisms
to adapt and respond to their environment.
And in trees that grow for thousands
of years with long generation cycles,
they can use any help they can get
to remain evolutionarily spry.
But scientists don't have a definitive answer to the
why these genomes are so big yet.
But doing these kinds of studies and sequencing these trees
can be an important step towards figuring it out.
Genomes can be really big.
And so can campaigns for good.
You may have heard about the huge Team Trees collaboration
on YouTube already.
But if not, hundreds of creators from around the globe,
spearheaded by Mark Rober and Mr. Beast,
are campaigning to raise $20 million dollars by 2020
to plant 20 million trees.
The trees will be planted around the world
by the Arbor Day Foundation.
And I love that their goal is to plant
native species, which is great.
As of recording this video, the campaign
has already reached 12 million trees.
And that's awesome.
But I think that sometimes when people
hear that a campaign is doing well,
they think, OK, that's great.
They're good.
I don't need to donate.
But that's not true.
There are still lots of trees to go.
And every dollar counts.
You can find out more information
about the campaign in the description below.
Go forth and plant some trees.
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