They encode the molecules that make up your body, from the keratin in your toenails, to the collagen at the tip of your nose, to the dopamine surging around inside your brain.

その遺伝子は体を作り上げている物質―

Other species have genes of their own.

足の爪のケラチンから 鼻の先のコラーゲン― までコード化しています

A spider has genes for spider silk.

（ドーパミン[誤り： タンパク質ではないのでコード化できない]）

An oak tree has genes for chlorophyll, which turns sunlight into wood.

他の種には独自の遺伝子があります

So where did all those genes come from?

クモにはその糸の遺伝子があります

It depends on the gene.

オークには太陽光線を木へと変える 葉緑素の遺伝子があります

Scientists suspect that life started on Earth about 4 billion years ago.

さて こういった遺伝子は どこから来たのでしょうか？

The early life forms were primitive microbes with a basic set of genes for the basic tasks required to stay alive.

それは遺伝子によります

They passed down those basic genes to their offspring through billions of generations.

科学者は約40億年前に地球上に 生命が誕生したと考えています

Some of them still do the same jobs in our cells today, like copying DNA.

初期の生命体は 原始的な微生物で―

But none of those microbes had genes for spider silk or dopamine.

生きていくために必要最低限の 遺伝子を一揃い持っていました

There are a lot more genes on Earth today than there were back then.

この基本となる遺伝子を 何十億もの世代を経て

It turns out that a lot of those extra genes were born from mistakes.

子孫に残してきたのです

Each time a cell divides, it makes new copies of its DNA.

DNAを複写する働きの様に 今でも 同じ働きをするものがあります

Sometimes it accidentally copies the same stretch of DNA twice.

しかしクモの糸（やドーパミン[誤]）の遺伝子を持つ 微生物はいませんでした

In the process, it may make an extra copy of one of its genes.

当時と比べると現在は 多様な遺伝子が存在しています

At first, the extra gene works the same as the original one.

実はこういった遺伝子の多くはミスから 生じたことが判明したのです

But over the generations, it may pick up new mutations.

細胞は分裂するたびに 新たなDNAのコピーを行います

Those mutations may change how the new gene works, and that new gene may duplicate again.

その際に誤って同じDNAの コピーを２度行うことがあるのです

A surprising number of our mutated genes emerged more recently; many in just the past few million years.

この過程でDNAを余分に コピーしてしまうのです

The youngest evolved after our own species broke off from our cousins, the apes.

最初はこの余分な遺伝子も 元の遺伝子と同じ働きをします

While it may take over a million years for a single gene to give rise to a whole family of genes,

しかし世代を経ていくと 新たな変異が加わって

scientists are finding that once the new genes evolve, they can quickly take on essential functions.

こういった変異が 新しい遺伝子の働きを変え

For example, we have hundreds of genes for the proteins in our noses that grab odor molecules.

新たな遺伝子が 再びコピーされます

The mutations let them grab different molecules, giving us the power to perceive trillions of different smells.

変異した遺伝子の数は 予想以上に多いことが判明しました;

Sometimes mutations have a bigger effect on new copies of genes.

多くはここ数百万年ほど前に起きたことです

They may cause a gene to make its protein in a different organ, or at a different time of life, or the protein may start doing a different job altogether.

最も新しいものはヒトが類人猿から 枝分かれした頃です

In snakes, for example, there's a gene that makes a protein for killing bacteria.

新しい遺伝子が生まれてから 遺伝子ファミリーとなるには

Long ago, the gene duplicated and the new copy mutated.

百万年以上もの時間がかかるものの

That mutation changed the signal in the gene about where it should make its protein.

ひとたび新しい遺伝子が発達すると

Instead of becoming active in the snake's pancreas, it started making this bacteria-killing protein in the snake's mouth.

基本的な機能となっていきます

So when the snake bit its prey, this enzyme got into the animal's wound.

例えば ヒトは鼻に匂いの分子を取り込む

And when this protein proved to have a harmful effect, and helped the snake catch more prey, it became favored.

数百ものタンパク質の遺伝子を持っています

So now what was a gene in the pancreas makes a venom in the mouth that kills the snake's prey.

この変異のおかげで 多様な分子をとらえられるため

And there are even more incredible ways to make a new gene.

一兆種類もの匂いを 嗅ぎ分けることができます

The DNA of animals and plants and other species contain huge stretches without any protein coding genes.

変異が大きな影響を もたらすこともあります

As far as scientists can tell, it's mostly random sequences of genetic gibberish that serve no function.

そのおかげで遺伝子が 別の臓器でタンパク質を作り出すことも

These stretches of DNA sometimes mutate, just like genes do.

あるいは 別の時期に起きるようになったり

Sometimes those mutations turn the DNA into a place where a cell can start reading it.

タンパク質が全く異なる 働きを始める事もあります

Suddenly, the cell is making a new protein.

例えばヘビにはバクテリアを殺す タンパク質の遺伝子があります

At first, the protein may be useless, or even harmful, but more mutations can change the shape of the protein.

かつて その遺伝子をコピーした時に 新たなコピーが変異を起こしました

The protein may start doing something useful, something that makes an organism healthier, stronger, better able to reproduce.

この変異が遺伝子の信号を変えてしまい

Scientists have found these new genes at work in many parts of animal bodies.

タンパク質を作り出す場所を 変えてしまいました

So our 20,000 genes have many origins, from the origin of life, to new genes still coming into existence from scratch.

膵臓で活動するのではなく

As long as life is here on Earth, it will be making new genes.

口内でバクテリアを殺す タンパク質を作り始めたのです