Your body typically regulates the speed at which your cells divide, but sometimes, cancer cuts the brake lines,

你的身體調控著你細胞的分裂速度，但有時候，癌症把煞車器拆掉，

and your cells divide too quickly, accumulating mutations that cause them to veer away from their original function, form dangerous tumors, and land you in the hospital.

接著你細胞就會分裂過快，累積突變並偏離原本的細胞功能，形成危險的腫瘤，並使你住院。

Cancer is basically an inability of the body to control the speed at which cells divide.

癌症基本上來說就是身體無法控制細胞分裂的速度。

When cells divide too quickly, they can often accumulate mutations that cause them to ignore their original function in the body, forming tumors.

當細胞分裂太快，他們經常會累積突變，忽略了他們在身體內原本的功能，形成腫瘤。

In turn, these tumors may interfere with the natural processes of the body, such as digestion and respiration, potentially leading to death.

這些腫瘤也可能干擾身體的正常作用，例如消化與呼吸作用，甚至會導致死亡。

Typically, your body has a number of genetic mechanisms to control how fast your cells divide.

一般來說，你的身體有很多基因機制來控制你細胞分裂的速度。

One of these genes is BRCA1, which stands for breast cancer susceptibility gene 1.

其中一種基因是 BRCA1，也就是乳腺癌易感基因 1 的簡寫。

BRCA1 belongs to a class of genes called tumor suppressor genes.

BRCA1 屬於一種腫瘤抑制基因。

Tumor suppressor genes are involved in regulating how fast a cell divides.

腫瘤抑制基因與控制細胞分裂速度有關。

Normally, cell division follows an orderly process called the cell cycle, which is basically the life cycle of a cell.

正常來說，細胞分裂遵循的是一個有秩序的程序，也就是細胞週期，基本上來說即是一個細胞的生命週期。

Within the cell cycle is a series of checkpoints, where proteins, such as the one produced by BRCA1, regulate how fast the cell may proceed.

在細胞週期中，有一系列的檢查站，讓蛋白質，像是由BRCA1製造的那種來調控細胞分裂的速度。

How does it do this?

它怎麼辦到的？

BRCA1 helps repair some forms of mutation in your DNA.

BRCA1 幫忙修復你 DNA 中的某些突變。

If your DNA is damaged, BRCA1 keeps the cell from dividing until the mutation is repaired.

如果你的 DNA 受到損壞，BRCA1 會阻止細胞分裂直到突變被修復了才繼續。

You have two copies of the BRCA1 gene in every cell of your body.

你有兩份 BRCA1 基因在你身體的所有細胞內。

One copy you inherited from Mom, the other from Dad.

一份是從媽媽遺傳而來，另一份則是從爸爸。

This redundancy is a good thing because you only need one functioning BRCA1 gene in a cell to regulate the cell cycle.

多一份是一件好事，因為你的細胞內只需要一份有功能的 BRCA1 基因來調控細胞週期。

But it's important to note that while these copies have a similar function they're not necessarily the same.

但重要的是，雖然這兩份基因有類似的功能，它們卻不完全一樣。

In fact, there are hundreds of variations, or alleles, of BRCA1.

事實上，BRCA1 有上百種變種或等位基因。

Some regulate the cell cycle more effectively than others.

有些能夠更有效的調控細胞週期。

In other words, some people are born with better regulating and repair mechanisms than others.

換句話說，有些人生來就有比他人更好的調節與修復機制。

And in some cases, mutations may render BRCA1 ineffective.

在某些情況下，突變可能導致 BRCA1 失效。

When this happens, cells with damaged DNA are allowed to divide.

當這種情況發生時，DNA 損壞的細胞會進行分裂。

As they divide, these cells may accumulate additional mutations.

當它們分裂時，這些細胞會累積額外的突變。

These mutations may cause the cell to become less specialized and stop performing its original function in the tissue.

這些突變可能使細胞，變得不容易被認出，並停止原先在組織中的功能。

If this occurs, then there's a greater chance they'll develop into cancer cells.

如果這件事發生，有很大的機會這些細胞會發展成癌症細胞。

While we all have the gene, such as BRCA1, that can cause cancer, it's only when these genes fail at their function that problems develop.

雖然我們都有這基因，像是 BRCA1，會造成癌症，但唯有當這些基因失去原先功能時，問題才會產生。

Having an ineffective or mutated version of BRCA1 can increase your susceptibility to cancer, much like driving with bad brakes increases the risk of an accident.

擁有無用或是突變的 BRCA1 會增加你得癌症的可能性，就很像駕駛一輛煞車壞掉的車會增加車禍的風險一樣。