But what truth is there to this?

但為什麼呢？

It turns out that one of the major contributors to hair loss is sex linked.

事實上，其中一個導致禿頭的原因與性別有關。

Humans have forty-six chromosomes of DNA, of which two help determine your sex, the "X" and the "Y" chromosome.

人類 DNA 有 46 條染色體，其中兩條決定你的性別，X 與 Y 染色體。

If you're a female you have two "X" chromosomes, but if you're a male you have an "X" and a "Y" chromosome.

女性擁有兩條 X 染色體，而男性擁有一條 X 染色體與一條 Y 染色體。

Studies show that the most influential hair-loss gene is located on the "X" chromosome only.

研究顯示造成禿頭的基因位於 X 染色體上。

What does this mean?

這代表什麼？

Well if you're a male you get an "X" chromosome from your mother, but must receive a "Y" chromosome from your father.

男性會從母親那得到其中一個 X 染色體，但是一定會從父親那得到 Y 染色體。

Because if you got your father's "X" chromosome you would be a female.

因為如果是從父親那得到 X 染色體，那你就會是女性。

So if one of your mothers "X" chromosomes has this hair loss gene you have a 50/50 chance of getting it from her.

如果母親的其中一個染色體有禿頭基因，你就有一半的機會禿頭。

In this way, hair loss is partially hereditary and passed through the maternal side for males.

因此對男性來講，禿頭基因是由母親遺傳決定的。

Females, on the other hand must get two copies of this gene, one on each "X" chromosome in order to physically express it.

而女性則必須得到分別位於兩個 X 染色體上的禿頭基因才會禿頭。

So if your mother does express these traits it means she will be passing an affected "X" chromosome to you.

因此如果你的母親禿頭，你就一定會得到禿頭基因。

But why do we say to look at your mother's father?

但是為什麼是要看祖父有沒有禿頭？

Well, if he has visible male pattern baldness then your mother has at least one copy of the affected "X" chromosome from him,

因為如果祖父禿頭，你的母親至少會有一個禿頭基因。

because in order to have a daughter he must have passed on his "X" chromosome, not his "Y".

因為女兒一定會得到父親的 X 染色體，而不是 Y 染色體。

The thing to note here is that this is just one of the contributors to hair-loss and while its thought to be the most significant,

雖然這被認為是最重要的因素，但這只是許多造成禿頭的因素之一。

many studies have found other hair linked genes which aren't sex linked at all.

許多研究指出，其他造成禿頭的基因與性別無關。

Including some on the "Y" chromosome, meaning they can be transferred from both the mother and the father.

期中包含一些在 Y 染色體上的基因，也就是說父母都有可能是你禿頭的原因

On top of this, some studies have shown correlations between age, exercise, nutrition and even stress levels.

另外，研究指出其他因素，譬如年齡、運動、飲食，甚至壓力都有影響。

So while a quick check of your mom's dad's hair maybe an indicator for future hair loss, a head full of hair on Grandpa's head does not guarantee you are in the clear.

所以當你察看祖父是否禿頭時，也許可以預判自己未來是否也會禿頭。但是就算祖父頭髮很多，也不保證你能保持頭髮茂密。

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