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

曼德尔的豌豆中的基因知识 - Hortensia Jiménez Díaz

Translator: Andrea McDonough Reviewer: Bedirhan Cinar

翻译人员: Haocong Lu 校对人员: Cissy Yun

These days scientists know

目前，科学家们了解到人们是如何

how you inherit characteristics from your parents.

从父母那里遗传到各种特征

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

他们能够计算

拥有具体特征

or getting a genetic disease

或者患有遗传病的机率

通过他们

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

从父母或家族史得到的信息

但这是如何成为可能的呢？

But how is this possible?

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

为了理解特征如何

从一个生物遗传到它的后代

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

我们需要回溯到19世纪

and a man named Gregor Mendel.

去看一个叫乔治·孟德尔的人

Mendel was an Austrian monk and biologist

孟德尔曾是一个奥地利的修道士

who loved to work with plants.

他是一个喜欢研究植物的生物学家

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

通过他在修道院的花园

培育豌豆的经历

he discovered the principles that rule heredity.

他发现了掌控遗传的定律

在一个最为经典的例子当中，

In one of most classic examples,

Mendel combined a purebred yellow-seeded plant

孟德尔杂交了一株纯种的黄粒植株

with a purebred green-seeded plant,

和一株纯种的绿粒植株，

and he got only yellow seeds.

最终他只得到了黄色的种子。

He called the yellow-colored trait the dominant one,

他把这个黄色特征称为显性特征

because it was expressed in all the new seeds.

因为所有的新种子当中都表现出了这个特征。

然后他让这个新的黄色杂种植株自交

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

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

在第二代中，

他得到了黄色和绿色的种子

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

这意味着绿色特征曾被

显性特征，黄色所掩盖

He called this hidden trait the recessive trait.

他称这个被掩盖的特征为隐性特征

From those results, Mendel inferred

通过那些结果，孟德尔推断

that each trait depends on a pair of factors,

每一种特征取决于一对因素，

one of them coming from the mother

其中一个因素来自于母亲

and the other from the father.

另一个来自于父亲

Now we know that these factors are called alleles

现在我们知道了这些因素被称作等位基因

and represent the different variations of a gene.

并且表现了一个基因的不同变化

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

取决于孟德尔在每一个种子中

发现的等位基因

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

我们能够得到我们称作纯合子的豌

当两个等位基因都是相同的，

而我们称某种豌豆为杂合子

and what we call a heterozygous pea,

当两个等位基因是不同

when the two alleles are different.

This combination of alleles is known as genotype

这种等位基因的组合被称为是遗传型

and its result, being yellow or green,

并且它的结果，黄色或绿色，

is called phenotype.

被称为表现型

To clearly visualize how alleles are distributed amongst descendants,

为了清晰地观察等位基因如何

在后代当中分布，

we can a diagram called the Punnett square.

我们可以使用一个叫庞氏表的图表

You place the different alleles on both axes

你可以把不同的等位基因放置于两个坐标轴当中

and then figure out the possible combinations.

然后你计算出可能的组合。

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

让我们以孟德尔的豌豆为例。

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

让我们把显性黄色等位基因写成大写的“Y”

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

隐性绿色等位基因写成小写的“y”。

The uppercase Y always overpowers his lowercase friend,

大写的“Y”总是能够主宰小写的“y”，

so the only time you get green babies

所以你得到绿色种子唯一的机会

is if you have lowercase Y's.

是当你有两个“y”的等位基因。

在孟德尔实验的第一代当中，

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

妈妈，黄色纯合子豌豆

将会给每一个豌豆宝宝一个黄色的显性等位基因，

will give each pea kid a yellow-dominant allele,

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

爸爸，绿色纯合子豌豆

将会提供一个绿色隐性等位基因。

So all the pea kids will be yellow heterozygous.

所以，所有的豌豆宝宝都是黄色杂合子豌豆

Then, in the second generation,

然后，在第二代，

两个杂合子宝宝结合，

where the two heterozygous kids marry,

他们的孩子们可以拥有任意一种上述的三种可能基因型，

their babies could have any of the three possible genotypes,

展现两种可能的表现型

showing the two possible phenotypes

in a three-to-one proportion.

是以三比一的比例

But even peas have a lot of characteristics.

但即使是豌豆也有许多特性，

For example, besides being yellow or green,

举例来说，除了黄色或绿色，

peas may be round or wrinkled.

豌豆还可以是园粒或皱粒，

So we could have all these possible combinations:

所以我们可以拥有所有这些可能的组合：

round yellow peas, round green peas,

黄色圆粒豌豆，

绿色圆粒豌豆，

黄色皱粒豌豆，

wrinkled yellow peas, wrinkled green peas.

和绿色皱粒豌豆

To calculate the proportions for each genotype and phenotype,

为了计算每种基因型和表现型的比例，

we can use a Punnett square too.

你可以用庞氏表

当然，这会使它变得稍微更复杂些

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

And lots of things are more complicated than peas,

还有许多东西比豌豆更复杂，

like, say, people.

比方说人类

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

目前科学家们了解了更多

关于基因和遗传的事情

这里还有许多其他的方法

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

将一些特性继承下去

但是，这都起源于孟德尔和他的豌豆

But, it all started with Mendel and his peas.