How Mendel's pea plants helped us understand genetics - Hortensia Jiménez Díaz

孟德爾的豌豆如何幫助我們瞭解遺傳學？ - Hortensia Jiménez Díaz

Translator: Andrea McDonough Reviewer: Bedirhan Cinar

譯者: Hao-Wei Chang 審譯者: Jephian Lin

These days scientists know

現在科學家知道

how you inherit characteristics from your parents.

你的性狀遺傳自父母

They're able to calculate probabilities of having a specific trait

他們可以藉由

從父母或家族史的資訊

or getting a genetic disease

計算出你

獲得到特定性狀

according to the information from the parents and the family history.

或是得到遺傳性疾病的機率

但這是怎麼做到的呢？

But how is this possible?

To understand how traits pass from one living being to its descendants,

要瞭解性狀如何

代代相傳

we need to go back in time to the 19th century

我們必須回到 19 世紀

and a man named Gregor Mendel.

從一個叫做格雷戈爾．孟德爾說起

Mendel was an Austrian monk and biologist

孟德爾是奧地利的修士和生物學家

who loved to work with plants.

他喜歡用植物作實驗

By breeding the pea plants he was growing in the monastery's garden,

藉由在修道院庭園中

雜交豌豆

he discovered the principles that rule heredity.

他發現遺傳學的法則

其中一個經典的例子是：

In one of most classic examples,

Mendel combined a purebred yellow-seeded plant

孟德爾將純種黃皮的豆子

with a purebred green-seeded plant,

和純種綠皮的豆子雜交

and he got only yellow seeds.

而只得到黃皮的豆子

He called the yellow-colored trait the dominant one,

他把黃色種皮這個性狀稱為顯性

because it was expressed in all the new seeds.

因為它在表現在所有子代

他接著讓黃種皮的子代自交

Then he let the new yellow-seeded hybrid plants self-fertilize.

And in this second generation, he got both yellow and green seeds,

而在第二子代中

他得到綠色和黃色種皮的豆子

which meant the green trait had been hidden by the dominant yellow.

這表示綠色種皮這個性狀

被顯性的黃色種皮所隱藏

He called this hidden trait the recessive trait.

他將這個會被隱藏的性狀稱為隱性

From those results, Mendel inferred

孟德爾從上述結果中推斷

that each trait depends on a pair of factors,

每個性狀都取決於一對因子

one of them coming from the mother

其中一個來自母親

and the other from the father.

而另一個來自父親

Now we know that these factors are called alleles

現在我們知道這些因子稱為對偶基因

and represent the different variations of a gene.

它們代表一個基因的不同「版本」

Depending on which type of allele Mendel found in each seed,

依照孟德爾從種子中

發現的對偶基因

we can have what we call a homozygous pea, where both alleles are identical,

我們將具有相同對偶基因的豌豆

稱為同型合子

並將具有兩個不同對偶基因的豌豆

and what we call a heterozygous pea,

稱為異型合子

when the two alleles are different.

This combination of alleles is known as genotype

對偶基因的組合稱為基因型

and its result, being yellow or green,

而它所造成黃色或綠色的結果

is called phenotype.

稱為表現型

To clearly visualize how alleles are distributed amongst descendants,

為了要清楚的瞭解對偶基因

如何分散到子代

we can a diagram called the Punnett square.

我們可以用一個稱為棋盤格法的圖表

You place the different alleles on both axes

你只要將不同的對偶基因列在軸線上

and then figure out the possible combinations.

你就能知道它們可能的組合形式

Let's look at Mendel's peas, for example.

我們用孟德爾的豌豆作例子

Let's write the dominant yellow allele as an uppercase "Y"

我們可以用大寫的 Y 表示顯性的黃色

and the recessive green allele as a lowercase "y."

小寫的 y 表示隱性的綠色

The uppercase Y always overpowers his lowercase friend,

大寫的 Y 永遠比小寫的 y 更具決定性

so the only time you get green babies

所以只有在兩個小寫的 y 出現時

is if you have lowercase Y's.

你才會得到綠色的子代

在孟德爾所得到的第一代中

In Mendel's first generation, the yellow homozygous pea mom

黃色同型合子的豌豆母親

給與每個子代一個顯性黃色的對偶基因

will give each pea kid a yellow-dominant allele,

and the green homozygous pea dad will give a green-recessive allele.

而綠色同型合子的父親

會提供綠色隱性的對偶基因

So all the pea kids will be yellow heterozygous.

所以所有的子代 都是黃色的異型合子

Then, in the second generation,

然後在第二代

當兩個異型合子的子代配對時

where the two heterozygous kids marry,

它們的子代有三種可能的基因型

their babies could have any of the three possible genotypes,

和比例為 1 : 3 的

showing the two possible phenotypes

in a three-to-one proportion.

兩種表現型

But even peas have a lot of characteristics.

但即使是豌豆也有很多性狀

For example, besides being yellow or green,

除了黃色或綠色種皮外

peas may be round or wrinkled.

豌豆也可能是光滑或有皺摺的

So we could have all these possible combinations:

所以我們可以有這些可能組合：

round yellow peas, round green peas,

黃色光滑的豌豆

綠色光滑的豌豆

黃色皺摺的豌豆

wrinkled yellow peas, wrinkled green peas.

和綠色皺摺的豌豆

To calculate the proportions for each genotype and phenotype,

你仍然可以用棋盤格法

we can use a Punnett square too.

計算各種基因型和外表型的比例

當然，過程會更加複雜

Of course, this will make it a little more complex.

And lots of things are more complicated than peas,

而許多生物比豌豆更複雜

like, say, people.

例如：人類

These days, scientists know a lot more about genetics and heredity.

現在科學家對於

基因與遺傳瞭解的更多

而且有些性狀的

And there are many other ways in which some characteristics are inherited.

會有不同的遺傳方式

但這一切都始於孟德爾和他的豌豆

But, it all started with Mendel and his peas.