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

Prevoditelj: Leona Grujić Recezent: Petra Lauš

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

U našim stanicama, svatko od nas ima drugi set gena,

completely separate from the 23 pairs of chromosomes

potpuno odvojen od 23 para kromosoma

we inherit from our parents.

koje nasljeđujemo od roditelja.

And this isn’t just the case for humans—

To ne vrijedi samo za ljude,

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

već i za sve životinje, biljke i gljive

and nearly every multicellular organism on Earth.

i gotovo svaki višestanični organizam na Zemlji.

This second genome belongs to our mitochondria,

Taj drugi genom pripada našim mitohondrijima,

an organelle inside our cells.

organelima u našim stanicama.

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

Nisu u cijelosti dio nas, ali nisu ni potpuno odvojeni od nas,

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

pa zašto su toliko različiti od svega ostalog u našem tijelu?

Approximately 1.5 billion years ago,

Prije otprilike 1,5 milijardi godina,

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

znanstvenici smatraju da je jednostanični organizam progutao pretka mitohondrija

creating the predecessor of all multicellular organisms.

i tako je stvoren predak svih višestaničnih organizama.

Mitochondria play an essential role:

Mitohondriji igraju ključnu ulogu:

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

pretvaraju energiju iz hrane koju jedemo i kisika koji dišemo

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

u oblik energije koji naše stanice mogu koristiti, u molekulu zvanu ATP.

Without this energy, our cells start to die.

Bez te energije, naše stanice bi odumrle.

Humans have over 200 types of cells,

Ljudi imaju više od 200 tipova stanica,

and all except mature red blood cells have mitochondria.

i sve osim zrelih crvenih krvnih zrnaca imaju mitohondrije.

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

To je zato što crvena krvna zrnca prenose kisik,

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

koji bi mitohondriji iskoristili prije nego stigne na odredište.

So all mitochondria use oxygen and metabolites to create energy

Dakle, mitohondriji koriste kisik i metabolite kako bi stvarali energiju

and have their own DNA,

i imaju vlastiti DNK,

but mitochondrial DNA varies more across species than other DNA.

ali mitohondrijski DNK varira više od drugog DNK u različitim vrstama.

In mammals, mitochondria usually have 37 genes.

U sisavaca, mitohondriji obično imaju 37 gena.

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

U nekih biljaka, poput krastavaca, imaju do 65 gena,

and some fungal mitochondria have only 1.

dok mitohondriji nekih gljiva imaju samo 1.

A few microbes that live in oxygen-poor environments

Nekoliko mikroba koji žive u uvjetima siromašnim kisikom,

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

čini se da polako u potpunosti gube mitohondrije,

and one group, oxymonad monocercomonoides, already has.

a jedna grupa, oxymonad monocercomonoides, već ih je izgubila.

This variety exists because mitochondria are still evolving,

Ova raznolikost postoji jer se mitohondriji još razvijaju,

both in tandem with the organisms that contain them,

zajedno s organizmom koji ih sadrži,

and separately, on their own timeline.

ali i zasebno, vlastitim tempom.

To understand how that’s possible,

Da bismo shvatili kako je to moguće,

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

trebali bismo baciti pogled na ono što naši mitohondriji rade,

starting from the moment we’re conceived.

od trenutka začeća.

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

U gotovo svim vrstama, mitohondrijski DNK nasljeđuje se od samo jednog roditelja.

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

Kod ljudi i većine životinja, to je majka.

Sperm contain approximately 50 to 75 mitochondria in the tail,

Spermatozoidi imaju između 50 i 75 mitohondrija u repu,

to help them swim.

da bolje plivaju.

These dissolve with the tail after conception.

Rasprše se s repom nakon začeća.

Meanwhile, an egg contains thousands of mitochondria,

S druge strane, jajna stanica sadrži tisuće mitohondrija,

each containing multiple copies of the mitochondrial DNA.

a svaki ima više kopija mitohondrijske DNK.

This translates to over 150,000 copies of mitochondrial DNA

To znači da postoji više od 150 000 kopija mitohondrijske DNK

that we inherit from our mothers,

koje nasljeđujemo od majke,

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

a svaka od njih je nezavisna i može se neznatno razlikovati od drugih.

As a fertilized egg grows and divides,

Kako oplođena jajna stanica raste i razvija se,

those thousands of mitochondria are divvied up into the cells

te tisuće mitohondrija raspoređuju se u stanice

of the developing embryo.

embrija u razvoju.

By the time we have differentiated tissues and organs,

Kad dođemo do razlučivih tkiva i organa,

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

varijacije u mitohondrijskoj DNK nasumično su razbacane u našem tijelu.

To make matters even more complex,

Da bi sve bilo još kompliciranije,

mitochondria have a separate replication process from our cells.

mitohondriji imaju odvojeni proces replikacije od naših stanica.

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

Naše se stanice repliciraju diobom i mitohondriji završavaju u novim stanicama,

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

a sve to vrijeme se i sami stapaju i dijele,

on their own timeline.

vlastitim tempom.

As mitochondria combine and separate,

Kako se spajaju i razdvajaju,

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

odvajaju neispravnu DNK i manjkave mitohondrije.

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

Sve to znači da se nasumični odabir mitohondrijskog DNK vaše majke

you inherit at birth

koji nasljeđujete kad se rodite

can change throughout your life and throughout your body.

može mijenjati tijekom vašeg života i duž vašeg tijela.

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

Dakle, mitohondriji su dinamični i donekle neovisni,

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

ali također ih oblikuje i njihova okolina: mi.

We think that long ago,

Mislimo da su jednom davno

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

neki od njihovih gena prešli u genom njihovog domaćina.

So today, although mitochondria have their own genome

Danas, iako mitohondriji imaju vlastiti genom

and replicate separately from the cells that contain them,

i repliciraju se odvojeno od stanica koje ih sadrže,

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

ne mogu to bez uputa naše DNK.

And though mitochondrial DNA is inherited from one parent,

I iako se mitohondrijska DNK nasljeđuje od jednog roditelja,

the genes involved in building and regulating the mitochondria

geni koji su uključeni u izgradnju i regulaciju mitohondrija

come from both.

dolaze od oba.

Mitochondria continue to defy tidy classification.

Mitohondriji se i dalje odupiru jasnoj klasifikaciji.

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

Njihova se priča još odvija u svakoj našoj stanici,

simultaneously separate and inseparable from our own.

istovremeno odvojena i neodvojiva od naše.

Learning more about them can both give us tools

Njihovo proučavanje pružilo bi nam alate

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

za zaštitu ljudskog zdravlja u budućnosti i za učenje o našoj prošlosti.