Your DNA is constantly changing.
And if it weren't for genetic mutations,
evolution wouldn't exist.
So what would life be
like if that stopped?
DNA is short for deoxyribonucleic acid.
And even though 99% of your DNA
is the same as everybody else,
it's the instruction manual for
what makes you, you.
DNA is what makes up your genome.
Your genome contains three billion bases,
20,000 genes
and 23 pairs of chromosomes.
Half you inherit
from the sperm of your father
and the other half
from the egg of your mother.
DNA provides directions for
your body to make different proteins
you need for your health,
growth and development.
So if that genetic evolution stopped,
would this lead to the eventual
extinction of humankind?
Did I mention your DNA
is constantly mutating?
Well, before you get too excited,
no, I don't mean any X-Men
type of mutations.
Your DNA mutations are changes
that occur in the sequence of a gene.
Some of them are good for you.
Some of them are bad.
Most are neutral.
Mutations are a natural part
of DNA replication.
Most of the time,
your DNA sequences
replicate without any errors.
But sometimes mistakes happen.
Mutations occur when nucleotides,
the basic building blocks
of DNA, are added,
deleted or incorrectly exchanged
in a sequence.
Entire segments of DNA could translocate,
or move, from one chromosome
to another.
They could even be replicated
in an inverted structure
of the original sequence.
You could inherit genetic mutations
from your parents.
You could acquire them
from environmental
agents like ultraviolet radiation
and certain chemicals.
Your genes can even mutate by chance.
But your DNA does
have methods for recognizing
these imperfections.
Special repair enzymes cut out
the wrong pieces
and replace them with the right ones.
But some of these mistakes get through
and become permanent.
At this point,
your cells would no longer
recognize them as errors.
Mutations in your body's cells
could impact your life,
development and well-being.
These random,
unpredictable DNA mistakes
account for nearly two-thirds
of the mutations in cancers.
But in order to be passed on,
genetic variants would need to occur
through reproduction.
This is called hereditary variation.
And it's what makes evolution possible.
So if mutations in your DNA stopped,
you'd no longer benefit
from some of the mutations that occur.
If you're an athlete,
you won't get the so-called sports gene.
This mutation
in the ACTN3 gene affects
muscle fibers responsible
for fast tensing or flexing.
Geneticists have found
that elite sprinters and power athletes
are less likely
to have defective copies
of this gene than the general public.
Another example is a mutation
linked to higher levels
of good cholesterol.
A mutation in the gene
that produces the CETP protein
can cause a deficiency that could cause
a lower prevalence
of coronary heart disease.
But with all of the positive mutations
out of the picture,
you'd also no longer suffer
from negative mutations.
Genetic disorders like cystic fibrosis
wouldn't pass on to new generations.
And if our cells didn't mutate,
then cancers
would also cease to exist.
“You’re cancer-free.”
Without these conditions,
the human lifespan could increase.
But we'd be ushering in a new era of life
without biological evolution.
Natural selection only operates,
or doesn't operate,
after a mutation occurs.
If that mutation is beneficial
to the survival of a species,
it becomes more common over time.
That means we'd need to develop
other forms of evolution
to keep our species from dying out.
Meanwhile, the other animals
and plants would continue to evolve.
Maybe the food you eat today
would no longer be
substantial for survival.
Look at lactose tolerance.
Most mammals lose their ability
to digest lactose before adulthood.
But for many humans,
this ability persists.
This is due to a mutation
in the LCT gene.
10,000 years ago, our diets changed
profoundly with the domestication
of plants and animals.
People who were able to better digest
these new foods had a genetic advantage.
If we could no longer adapt to new diets,
we'd have to develop new technologies
to make food that could
sustain our species.
If we can already make lactose-free milk,
maybe there's no end to the ways
we can survive without genetic mutations.
But good or bad,
these little errors
are what makes us who we are.
Still, it wouldn't be as bad
as that time we made
your DNA disappear.
But that's a story for another WHAT IF.