The genes you don't get from your parents (but can't live without) - Devin Shuman

Translator: Fernando Cabana Reviewer: traduceTED USC

Inside our cells, each of us has a second set of genes

Cada un de nós temos un segundo conxunto de xenes nas nosas células

completely separate from the 23 pairs of chromosomes

separados dos 23 pares de cromosomas

we inherit from our parents.

que herdamos dos nosos pais.

And this isn’t just the case for humans—

Isto non só pasa nos humanos,

it’s true of every animal, plant, and fungus,

senón tamén en todo animal, planta ou fungo,

and nearly every multicellular organism on Earth.

e case calquera organismo pluricelular da Terra.

This second genome belongs to our mitochondria,

Este segundo xenoma pertence ás nosas mitocondrias,

an organelle inside our cells.

un orgánulo das nosas células.

They’re not fully a part of us, but they’re not separate either—

Non son de todo parte nosa, pero tampouco algo aparte.

so why are they so different from anything else in our bodies?

Entón, por que son tan diferentes do resto do noso corpo?

Approximately 1.5 billion years ago,

Hai aproximadamente 1500 millóns de anos,

scientists think a single-celled organism engulfed the mitochondria’s ancestor,

un organismo unicelular enguliu o antepasado das mitocondrias

creating the predecessor of all multicellular organisms.

e creou o predecesor de todos os organismos pluricelulares.

Mitochondria play an essential role:

As mitocondrias teñen un papel esencial:

they convert energy from the food we eat and oxygen we breathe

converten a enerxía do que comemos e do osíxeno que respiramos

into a form of energy our cells can use, which is a molecule called ATP.

nunha molécula, o ATP, que as nosas células poden empregar.

Without this energy, our cells start to die.

Sen esta enerxía, as células morren.

Humans have over 200 types of cells,

Os seres humanos temos máis de 200 tipos de células,

and all except mature red blood cells have mitochondria.

e todas teñen mitocondrias, agás as células vermellas maduras.

That’s because a red blood cell’s job is to transport oxygen,

Isto débese a que estas últimas se encargan de transportar osíxeno

which mitochondria would use up before it could reach its destination.

e, de teren mitocondrias, usaríano antes de chegar ao seu destino.

So all mitochondria use oxygen and metabolites to create energy

Todas as mitocondrias usan osíxeno e metabolitos para xerar enerxía

and have their own DNA,

e teñen o seu propio ADN,

but mitochondrial DNA varies more across species than other DNA.

pero o ADN mitocondrial varía entre especies máis que o resto de ADN.

In mammals, mitochondria usually have 37 genes.

Nos mamíferos, en xeral, as mitocondrias teñen 37 xenes.

In some plants, like cucumbers, mitochondria have up to 65 genes,

Nalgunhas plantas, como os cogombros, as mitocondrias teñen ata 65 xenes,

and some fungal mitochondria have only 1.

e mesmo hai mitocondrias en fungos que só teñen un.

A few microbes that live in oxygen-poor environments

Uns poucos microbios en medios pobres en osíxeno

seem to be on the way to losing their mitochondria entirely,

parecen encamiñados a perder as súas mitocondrias

and one group, oxymonad monocercomonoides, already has.

e un grupo, Oxymonadida monocercomonoides, xa perdeu as súas.

This variety exists because mitochondria are still evolving,

Esta variedade débese a que as mitocondrias seguen a evolucionar,

both in tandem with the organisms that contain them,

tanto en conxunto cos organismos que as conteñen

and separately, on their own timeline.

como individualmente, na súa propia liña temporal.

To understand how that’s possible,

Para entender como isto é posible,

it helps to take a closer look at what the mitochondria inside us are doing,

axuda botar unha ollada a que fan exactamente as nosas mitocondrias,

starting from the moment we’re conceived.

comezando pola nosa concepción.

In almost all species, mitochondrial DNA is passed down from only one parent.

Na práctica totalidade de especies, o ADN mitocondrial hérdase dun proxenitor.

In humans and most animals, that parent is the mother.

Nos humanos e na maioría de animais, hérdase da nai.

Sperm contain approximately 50 to 75 mitochondria in the tail,

Cada espermatozoide contén entre 50 e 75 mitocondrias na cola

to help them swim.

para axudarlle a nadar.

These dissolve with the tail after conception.

Estas mitocondrias disólvense xunto á cola na concepción.

Meanwhile, an egg contains thousands of mitochondria,

Mentres, un óvulo contén miles de mitocondrias,

each containing multiple copies of the mitochondrial DNA.

cadansúa con múltiples copias de ADN mitocondrial.

This translates to over 150,000 copies of mitochondrial DNA

En total, isto equivale a máis de 150 000 copias de ADN mitocondrial

that we inherit from our mothers,

que herdamos das nosas nais,

each of which is independent and could vary slightly from the others.

cada unha delas independente e potencialmente con lixeiras variacións.

As a fertilized egg grows and divides,

Ao crecer e dividirse o cigoto,

those thousands of mitochondria are divvied up into the cells

milleiros de mitocondrias repártense entre as células

of the developing embryo.

do embrión en desenvolvemento.

By the time we have differentiated tissues and organs,

Para cando temos tecidos e órganos diferenciados,

variations in the mitochondrial DNA are scattered at random throughout our bodies.

as variacións no ADN mitocondrial repártense ao chou nos nosos corpos.

To make matters even more complex,

Para complicar as cousas aínda máis,

mitochondria have a separate replication process from our cells.

as mitocondrias teñen un proceso de replicación á parte do das células.

So as our cells replicate by dividing, mitochondria end up in new cells,

Mentres que as nosas células se replican dividíndose,

and all the while they’re fusing and dividing themselves,

as mitocondrias acaban en novas células, á vez que, ao seu ritmo,

on their own timeline.

se fusionan e dividen.

As mitochondria combine and separate,

Ao combinarse e dividirse,

they sequester faulty DNA or mitochondria that aren’t working properly for removal.

illan ADN erróneo ou mitocondrias que non funcionan ben para eliminalas.

All this means that the random selection of your mother’s mitochondrial DNA

Isto significa que o conxunto aleatorio de mitocondrias da túa nai

you inherit at birth

que herdaches ao nacer

can change throughout your life and throughout your body.

pode variar ao longo da túa vida e tamén do teu corpo.

So mitochondria are dynamic and, to a degree, independent,

Entón, as mitocondrias son dinámicas e, ata certo punto, independentes,

but they’re also shaped by their environments: us.

pero tamén están moduladas polo seu medio: nós.

We think that long ago,

Coidamos que hai moito,

some of their genes were transferred to their host’s genomes.

algúns dos seus xenes se transferiron aos xenomas do seu hóspede,

So today, although mitochondria have their own genome

polo que hoxe, aínda tendo as mitocondrias o seu propio xenoma

and replicate separately from the cells that contain them,

e replicarse independentemente das células que as conteñen,

they can't do this without instruction from our DNA.

non son capaces de facelo sen instrucións do noso ADN.

And though mitochondrial DNA is inherited from one parent,

E a pesar de herdar o ADN mitocondrial dun só proxenitor,

the genes involved in building and regulating the mitochondria

os xenes involucrados en construír e regular as mitocondrias

come from both.

veñen de ambos.

Mitochondria continue to defy tidy classification.

As mitocondrias seguen a combater unha clasificación ordenada.

Their story is still unfolding inside of each of our cells,

A súa historia séguese a desenvolver en cada unha das nosas células,

simultaneously separate and inseparable from our own.

unha historia separada da nosa e, á vez, inseparable.

Learning more about them can both give us tools

Estudalas pódenos proporcionar ferramentas

to protect human health in the future, and teach us more about our history.

para protexer a saúde humana no futuro e coñecer máis sobre a nosa historia.