Why are human bodies asymmetrical? - Leo Q. Wan

Translator: Nika Kotnik Reviewer: Matej Divjak

Simetrija je povsod v naravi

Symmetry is everywhere in nature,

and we usually associate it with beauty:

in ponavadi jo povezujemo z lepoto:

a perfectly shaped leaf,

popolno oblikovan list,

or a butterfly with intricate patterns mirrored on each wing.

ali pa metulj z zapletenimi vzorci, enakimi na obeh krilih.

But it turns out that asymmetry is pretty important, too,

A izkaže se, da je tudi asimetrija precej pomembna,

and more common than you might think,

in bolj pogosta, kot si mislite,

from crabs with one giant pincer claw

od rakov z enimi velikimi kleščami

to snail species whose shells' always coil in the same direction.

do vrst polžev, katerih hiške se vedno zavijajo v isto smer.

Some species of beans only climb up their trellises clockwise,

Nekatere vrste fižola se vzpenjajo po ogrodju v smeri urinega kazalca,

others, only counterclockwise,

druge pa samo v nasprotni smeri,

and even though the human body looks pretty symmetrical on the outside,

in čeprav je človeško telo na zunaj videti precej simetrično,

it's a different story on the inside.

je notri druga zgodba.

Most of your vital organs are arranged asymmetrically.

Večina tvojih vitalnih organov je urejenih asimetrično.

The heart, stomach, spleen, and pancreas lie towards the left.

Srce, želodec, vranica in trebušna slinavka ležijo bolj na levo.

The gallbladder and most of your liver are on the right.

Žolčnik in večina jeter sta na desni.

Even your lungs are different.

Celo tvoja pljuča so drugačna.

The left one has two lobes, and the right one has three.

Leva imajo dva lobusa in desna imajo tri.

The two sides of your brain look similar, but function differently.

Obe polovici možganov izgledata podobno, a delujeta na drugačen način.

Making sure this asymmetry is distributed the right way is critical.

Pomembno je, da je asimetrija razporejena na pravi način.

If all your internal organs are flipped, a condition called situs inversus,

Če so vsi tvoji organi obrnjeni zrcalno, kar imenujemo situs inversus,

it's often harmless.

je to pogosto neškodljivo.

But incomplete reversals can be fatal,

Nepopolni obrati pa so lahko smrtni,

especially if the heart is involved.

še posebej, če je vpleteno srce.

A od kod pride ta asimetrija,

But where does this asymmetry come from,

since a brand-new embryo looks identical on the right and left.

glede na to, da je nov zarodek videti enak na levi in desni.

One theory focuses on a small pit on the embryo

Ena teorija se osredotoča na majhen del embrija,

called a node.

ki se imenuje nodus.

Nodus je obdan z majhnimi laski, imenovanimi cilije,

The node is lined with tiny hairs called cilia,

ki se nagibajo stran od glave in divje plapolajo v isti smeri.

while tilt away from the head and whirl around rapidly,

all in the same direction.

This synchronized rotation pushes fluid from the right side of the embryo

Ta sinhronizacija potiska tekočino iz desne strani zarodka na levo.

to the left.

On the node's left-hand rim,

Na levem robu nodusa

other cilia sense this fluid flow

drugi bički zaznajo ta pretok tekočine

and activate specific genes on the embryo's left side.

in aktivirajo specifične gene na levi strani zarodka.

These genes direct the cells to make certain proteins,

Ti geni usmerjajo celice v izdelavo določenih beljakovin

and in just a few hours,

in samo v nekaj urah

the right and left sides of the embryo are chemically different.

sta leva in desna stran zarodka kemično drugačni.

Even though they still look the same,

Čeprav še vedno izgledata enako,

these chemical differences are eventually translated into asymmetric organs.

se te kemične razlike na koncu prevedejo v asimetrične organe.

Asymmetry shows up in the heart first.

Asimetrija se najprej pokaže na srcu.

It begins as a straight tube along the center of the embryo,

Začne se kot ravna cev v centru zarodka,

but when the embryo is around three weeks old,

a ko je zarodek star približno tri tedne,

the tube starts to bend into a c-shape

se cev ukrivi v obliko črke C

and rotate towards the right side of the body.

in se obrne proti desni strani telesa.

It grows different structures on each side,

Na vsaki strani zrastejo različne strukture,

eventually turning into the familiar asymmetric heart.

ki se na koncu spremenijo v nam znano asimetrično srce.

Meanwhile, the other major organs emerge from a central tube

Medtem se iz osrednje cevi razvijejo drugi organi

and grow towards their ultimate positions.

in proti svojim končnim pozicijam.

But some organisms, like pigs, don't have those embryonic cilia

A nekateri organizmi, naprimer prašiči, nimajo teh zarodkovih bičkov

and still have asymmetric internal organs.

in imajo vseeno asimetrične notranje organe.

Could all cells be intrinsically asymmetric?

So morda vse celice naravno asimetrične?

Probably.

Najbrž.

Bacterial colonies grow lacy branches that all curl in the same direction,

Bakterijske kolonije rastejo v čipkastih vejicah, zavijajočih v isto smer,

and human cells cultured inside a ring-shaped boundary

in človeške celice, vzgojene v območju z obliko obroča,

tend to line up like the ridges on a cruller.

se razporedijo kot robovi na potici.

If we zoom in even more,

Če še bolj približamo,

we see that many of cells' basic building blocks,

vidimo, da so glavne sestavine celic,

like nucleic acids, proteins, and sugars, are inherently asymmetric.

kot so nukleinske kisline, beljakovine in sladkorji, vsi pravzaprav asimetrični.

Proteins have complex asymmetric shapes,

Beljakovine imajo zapletene asimetrične oblike,

and those proteins control which way cells migrate

in ti proteini določajo, v katero smer migrirajo celice

and which way embryonic cilia twirl.

in v katero smer se vrtijo bički embrija.

These biomolecules have a property called chirality,

Te biomolekule imajo lastnost imenovano kiralnost,

which means that a molecule and its mirror image aren't identical.

ki pomeni, da si molekula in njena zrcalna oblika nista identični.

Like your right and left hands, they look the same,

Poglejte levo in desno roko, izgledata enaki,

but trying to put your right in your left glove proves they're not.

a če poskušaš spraviti desno rokavico na levo, vidiš da nista.

This asymmetry at the molecular level is reflected in asymmetric cells,

Ta asimetrija na molekularni ravni se odraža v asimetričnih celicah,

asymmetric embryos,

asimetričnih zarodkih

and finally asymmetric organisms.

in končno asimetričnih organizmih.

So while symmetry may be beautiful,

Simetrija je morda lepa,

asymmetry holds an allure of its own,

a tudi asimetrija ima svoj čar,

ki ga najdemo v elegantnih zavojih,

found in its graceful whirls,

its organized complexity,

v njeni organizirani kompleksnosti

and its striking imperfections.

in njenih osupljivih nepopolnostih.