So say you have a clone or a secret identical twin
because you know that a twin or clone
is a genetically identical person to you, which is crazy!
But it’s true.
Anyway,so you have this clone or twin
What have your parents decide that it’s too much trouble to keep both of you
And so they give your clone to a
kind of sketchy traveling circus.
Now I know your parents probably wouldn’t actually do this,
but just roll with me for a minute.
So for the purposes of this example let’s just say
that you grew up living a normal suburban
American life while your clone grew up with less stability
and less access to nutritious food and less education.
But more exercise and more access
to sword swallowers
and bearded ladies.
And let’s say you guys are 50 years old, whatever,
you get together and have some lunch.
So you sit in there across the table from your clone.
What do you think you see?
Well for starters, Clone probably has a tattoo on its face.
And if Clone had stayed in the circus.
Clone probably, you know, professionally rides a unicycle over a tightrope,
so Clone is probably in pretty good shape.
But then again Clone probably smoked cigarettes and
probably was malnourished as a child so might be slightly shorter than you
By the same token, let’s say that
you’ve been eating sonic tater tots five days a week since 1992
so you’re looking a little bit tubby.
Plus, you spent the last 20 years at a really stressful job that puts you at risk
for all kinds of weird health complications.
So at 50, you and Clone would probably look pretty different from one another.
But it turns out you don’t just look different.
You actually have become different.
Now, if some scientists looked at your genetic code
they would say that your DNA was still exactly the same as that other person.
That is to say, if your genome is a paragraph
all of the letters would be in the exact same word
But on another level
there would be a huge difference
and if we extend this metaphor
we can say that the letters are in the same order
but the spaces in the punctuation are all in different places
of course completely
potentially changing the message of that paragraph.
The study of this genetic punctuation that I’m talking about
is called epigenetics which literally means above genetics
The epigenome doesn’t change your DNA
But it decides how much or whether some genes are
expressed in different cells in your body
Epigenetics looks at what happens to
your genes over the course of your life
and whether those changes could be passed down to your children
or even your grandchildren
So here’s the way epigenetics works
you have billions of cells in your body
and they each contain your DNA
the same exact blueprint of your genetic code
But just because they have the DNA
it doesn’t mean that they know what to do with it
They need outside instruction from these
little carbon and hydrogen compounds called methyl groups.
The way these Methyl groups control the genome is by binding to a gene
and saying do not express this gene.
The methyl groups bind differently to your genome
and a skin cell versus say a tongue cell or an eyeball cell
and that is one of the ways that a cell knows that
hey, I’m the skin cell or hey，I’m an eyeball cell hey， I’m a muscle Cell.
In addition to Methyl groups epigenetics is also controlled by histones
which are proteins that are basically the spools that DNA winds itself around.
Histones can change how tightly or loosely the DNA is wound around them
if they’re more loosely wound the genes can express more
and if they’re more tightly round than they express less
so whereas the Methyl groups are more like a switch
the histones are more like a knob
Every cell and your body
has a distinct methylation and histone pattern
and that is what gives every cell its marching orders.
Think of your genome the DNA is the actual hardware of the computer
While the epigenome is more like the software which tells the hardware what to do.
The genome is what’s going to be doing all the work
but the epigenome is going to be telling it what to do.
So the hardware of your DNA
is going to be the same throughout your entire life,
but these epigenetic tags do change throughout your life
And they decide what genes get expressed or not.
Now epigenetic information in a cell isn’t permanent
it can change throughout your life, and it can be hereditary
And it can change over time
especially when your body is going through a lot of changes
like say during puberty
A bunch of Methyl groups kick in they’re like
Okay so you guys over here
You’re gonna have to start growing hair
and you guys over here
I really need you guys to get behind
giving this guy’s some really horrible acne
or like when you get pregnant which hopefully I won’t
but when you do your epigenome has to be like
alright guys everything’s about to get a whole lot bigger in here
And we’re gonna have to pass something the size of like a miriam Webster’s dictionary
through that little pipe over there
So let’s get this thing done
but it’s not just these dramatic times
when the epigenome is changing
It changes suddenly throughout our entire lives
and it changes based on a lot of environmental factors
like what we do what we eat
what we smoke and how stressed out we are in a daily basis
Scientists have found that things like a bad diet
can actually lead to Methyl groups binding to the wrong place and making mistakes.
And with those bad instructions
cells become abnormal and become a disease
and then basically all hell breaks loose
and you get cancer or something.
Epigenetics is a very young science
though we’ve known about the epigenome since the 1970s
It’s only in the last 20 years that we’ve even known
what effect these epigenetic tags are having on our DNA.
And even after they got all that business straight
Scientists still thought
that all of our epigenetic tags were stripped off of our genome
before they were passed on to our children
So if you started smoking 10 packs a day when you were 10 years old
that would certainly be a horrible health decision for you
But you wouldn’t necessarily be harming your unborn children in any measurable way.
However the thinking on that is changing pretty rapidly
because it’s true that a lot even most of the
epigenetic information from a parent
is stripped off of the embryos genome in the first few days
and fresh ones are created specifically for this new person.
However some of these tags get stuck on the genome and are passed down from generation to generation
但是 其中一些标签留在基因组上 并世代相传
and it just so happens that the more they study this the more it looks like
bad epigenetic information is being passed from generation to generation
and this is a whole new way to think about how we pass information between generations
Your grandmother was making dietary decisions that affect you today
As we experience all these new strange epidemics diabetes autoimmune disorders cancers
that weren’t appearing in previous generations
全新的奇怪的流行病 糖尿病 自身免疫性疾病
It’s starting to look like these may be caused by
epigenetic information passed down from our parents
I know it’s such an unbelievable Buzzkill
There is no point in our lives when we can do anything
without guilt anymore
The discovery that the environmental factors the parent experiences
can be passed down from generation to generation was sparked in the 1980s
and this happen when some scientists were looking at the birth and death records of some people
who lived in nineteenth-century Sweden
as is a weird place to find a genetic revolution but there it is
wasn’t just any place in Sweden
It was in Norrbotten，which is the Northernmost County in Sweden
which is literally in the arctic circle
and despite the fact that norrbotten was literally the worst place
you could possibly choose to live in Sweden，
there were some people living there in the 1800s
and they were completely cut off from the rest of the world
Let me clarify
these people were isolated
like if they didn’t have a good crop year people died
No, it wasn’t ideal
but you know they didn’t ask me my opinion
So I’m not giving it
So anyway these people subsisted entirely on what they grew when the animals that they raised
and like I said sometimes they starved
but sometimes they had huge bountiful years of plenty
and what happened people totally went ape crackers.
I mean of course they did because they were so freakin hungry
我是说 他们当然会这样 因为他们饿坏了
and then all of a sudden there was all this damn food everywhere.
Anyway there was a public health specialist
who was looking at the effects of the people who grew up in the really bad starving periods of time
versus the people who grew up in the
eat all you can at the smorgasbord years.
You might already be guessing what they found out.
people who went from relatively slim pickins
to feed your face until you have to barf and
then do it all over again in a single season.
Those people dead at an average of six years sooner than they’re starved out counterparts,
and you know it sucks
, so do their kids so do their kids‘ kids
So of course now we all know
and we’re all going to stop doing unhealthy things starting today
Unless the damage is already done the damage is
almost certainly already done, but hey
损害几乎一定是已经无法挽回了 但是 嘿
epigenetics brings good tidings along with bad ones
We now know that certain types of cancer are caused by
misplaced epigenetic tags and
scientists are now developing drugs that can silence the bad genes
that were supposed to be turned off in the first place
additionally until recently we thought
此外 直到最近 我们还以为
that genes were the end all
and be all of who you got to be.
They were your blueprint and you couldn’t escape them.
This outlook is not just kind of depressing and
also alludes to a yucky sort of social prejudice
because when you look at data
without considering social and epigenetic factors
it might look like people with less money are less intelligent
So just like 15 years ago there were scientists saying things in public
mind you like some people just have good genes for intelligence
and it just so happens that the poor people don’t all it’s so sad too bad poor people
恰好穷人就没有这种基因 太令人沮丧了 可怜的穷人
But you have bad genes
Well it turns out that that is not even a little bit true
Not only are there a huge variety of social factors
that affect how well people do on intelligence tests
but a genetic trait is also, not just a product of genes
it’s also a product of environment
any one person’s genome was determined by
any number of decisions made by any number of their ancestors.
And right now you are making decisions
that are going to affect people who are alive long after you were dead
no pressure or anything and
so I’m glad you’ve watched this
because when you and your clone are in your 60s
And you sit down have lunch, and he brings his son and his son has a tattoo on his face
He did not inherit that from you.
This is Hank Green from the Scishow. We hope you learned something.