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DNA检测关于追溯祖先的启示 – 译学馆
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DNA检测关于追溯祖先的启示

What can DNA tests really tell us about our ancestry? - Prosanta Chakrabarty

他们总是问我这个难题 “我们从哪儿来?”
Two sisters take the same DNA test.
一对姐妹进行了相同的DNA检测
The results show that one sister is 10% French, the other 0%.
结果是其中一个有10%的法国血统 而另一个没有
Both sisters share the same two parents,
而她们有相同的父母
and therefore the same set of ancestors.
因此也有着相同的祖先集
So how can one be 10% more French than the other?
那么为什么一个人会比另一个多10%的法国血统呢?
Tests like these rely on our DNA to answer questions about our ancestry,
像这样的检测 依靠我们的DNA来解答关于我们祖先的问题
but our DNA actually can’t tell us everything
但是我们的DNA 事实上并不能充分解答关于我们祖先的问题
about who we are or where we’re from.
关于我们是谁或是我们从哪儿来的
DNA tests are great at answering some questions,
DNA检测可以很好地解决一些问题
like who your parents are, but can provide baffling results to others,
比如你的父母是谁 但是对于另一些问题则束手无策
like whether you have ancestors from a particular region.
比如你的祖先是否是从一个特定地区来的
To understand why, it helps to know where our DNA comes from in the first place.
为了了解其中的原因 首先我们有必要知道我们的DNA来自于何处
Each person’s DNA consists of about 6 billion base pairs
每个人的DNA由大约60亿个碱基对组成
stored in 23 pairs of chromosomes— 46 total.
它们被储存在23对染色体中 也就是一共46个
That may seem like a dizzying amount of information,
这似乎是一个令人眼花缭乱的信息量
but 99% of our genome is shared among all humans.
但是我们基因组中的99%是所有人类所共有的
The remaining 1% contains everything distinct about an individual’s ancestry.
剩余的1%包含了所有关于个体祖先独特的信息
Commercial DNA tests utilize less than 1% of that 1%.
商业DNA检测利用的 还不到这1%的1%
One chromosome in each pair comes from each parent.
每对染色体都是一条来自父亲 一条来自母亲
These halves join at conception: when a sperm and egg,
它们在受孕时结合在一起
each with only 23 chromosomes, combine.
当各自仅有着23条染色体的一个精子和卵子结合的时候
The story of our ancestry becomes muddled before conception.
我们祖先的故事在受孕前就开始变得混乱了
That’s because the 23 chromosomes in a sperm or egg
那是因为在一个精子或是卵子里的23条染色体
aren’t identical to the chromosomes of every other cell in the body.
和身体中其他细胞的染色体并不完全相同
As they go from a cell with 46 chromosomes to a sex cell with only 23,
当它们从一个有46条染色体的细胞变成只有23条染色体的性细胞时
the chromosomes within each pair swap some sections.
每对染色体中的一些部分发生了互换
This process is called recombination, and it means that every sperm or egg
这个过程被叫做重组 这意味着
contains single chromosomes that are a unique mash up of each pair.
每个精子或卵子都包含单个染色体 每对染色体都是独一无二的组合
Recombination occurs uniquely in each sex cell—
在每个性细胞发生的重组都是独特的
making two sisters’ chromosomes different not only from their parents’,
使得一对姐妹的染色体不仅和父母的不同
but from each other’s.
而且彼此之间也有差异
Recombination happens before conception,
重组在受孕前就发生了
so you get exactly half of your DNA from each parent,
所以你从父母双方各得到一半的DNA
but going further back things get more complicated.
但再往前追溯 事情就变得更复杂了
Without recombination, you would get 1/4 from each grandparent,
如果没有重组 你会从祖父母分别得到1/4的DNA
1/8 from each great-grandparent, and so on,
从曾祖父母得到1/8的DNA 以此类推
but because recombination happens every generation, those numbers vary.
但是因为每代都会发生重组 所以这些数字也有变化
The more generations removed an ancestor is,
你和祖先之间隔的代数越多
the more likely they won’t be represented in your DNA at all.
你的DNA中越有可能完全没有他们的影子
For example, without recombination,
举例来说 如果没有发生重组
just 1/64 of your DNA would come from each ancestor six generations back.
你的DNA只有1/64是来自于6代之前的每个祖先
Because of recombination, that number can be higher,
由于发生了重组 那个数字会变得更高
though we don’t know for sure how high— or it can as low as 0.
尽管我们不能确切地知道有多高 或者也可能为0
So one sister isn’t more French
因此姐妹中的一个有更多的法国血统
in the sense of having more ancestors from France.
并不意味者她有更多法国的祖先
Instead, the French ancestors are simply more represented in her DNA.
而是法国祖先在她的DNA中更具有代表性
But the story doesn’t end there.
故事到此还并没有结束
Tests don’t trace the DNA of the sisters’ actual French ancestors—
检测并不是追溯这对姐妹真实的的法国祖先
we don’t have access to the genomes of deceased individuals
我们没办法得到前几代
from previous generations.
已故个体的基因组
Instead, these results are based on a comparison
而这些结果是基于如今居住在法国的
to the DNA of people living in France today.
人们的DNA的比较所得到的
The tests look for genetic markers, or combinations of genetic markers.
DNA检测寻找遗传标记或遗传标记的组合
These markers are short sequences that appear in specific places.
这些标记是出现在特定位置的短序列
The sister deemed “more French” shares genetic markers
那个被认为有更多法国血统的姐姐或妹妹
with people currently living in France.
有着和现在居住在法国的人共同的标记
The assumption is that these shared markers indicate ancestors
我们假设这些共同的标记表明了
from the same place: France.
他们的祖先来自同一个地方:法国
It’s important to note that results are based on people
需要注意的是 这些结果是基于那些
who’ve had their genomes sequenced—
已经进行了基因组测序的人群而得到的
80-90% of which are of European descent.
这些人80-90%都具有欧洲血统
Many indigenous peoples are barely represented, if at all.
而许多原住民(如果有的话)几乎并不能被代表
The test won’t reveal heritage from
对于没有被录入数据库的人来说
people not represented in the database,
这项检测将不能反映他们的遗传数据
and shouldn’t be used to prove race or ethnicity.
也不应该被用于证明人种或者种族
And as more people get sequenced, your results might change.
随着更多的人被测序 你的结果也可能发生改变
Looking further back,
比如往前追溯
you may get a result like 2% Neanderthal.
你可能会得到有2%尼安德特人血统的结果
Though Neanderthals were a separate species from humans,
尽管尼安德特人是和人类不同的物种
that 2% doesn’t come out of the 99% of
那2%并不是从所有人类共有的
our genome shared among all humans,
也就是我们基因组99%中产生的
but the 1% that varies.
而是从那不同的1%中产生的
That’s because about 40,000 years ago,
这是因为大约40000年以前
certain human populations interbred with Neanderthals,
某些人类种群和尼安德特人发生了杂交
meaning some people alive today have Neanderthal ancestors.
意味着如今生活着的一些人的祖先是尼安德特人
Many Neanderthal ancestors, in fact:
事实上他们很多祖先都是尼安德特人
there are so many generations in 40,000 years
在40000年中有如此多的世代
that a single Neanderthal’s genetic contribution would be untraceable.
以至于单个尼安德特人的基因贡献率将会无迹可寻
You can be both 100% French and 2% Neanderthal—
你可以同时有100%的法国血统和2%的尼安德特人血统
though both come from the 1% of DNA that makes us different,
尽管都来自于那1%使我们不同的DNA
they’re accounting for different things.
但是它们解释了不同的事情
Looking for traces of our ancestry in our DNA gets complicated very quickly.
在我们的DNA中寻找我们祖先的痕迹很快就变得复杂
Both the way we inherit DNA and the information available for testing
不仅是我们继承DNA的方式 还有可用于检测的信息
makes it difficult to say certain things with 100% certainty.
都使以100%的确信说出某些事情变得很难
When you think of the discovery of DNA,you probably think of two names
当你想到DNA发现史的时候 你可能会想到两个名字
Watson and Crick
沃森和克里克
But there is a third answer scientist whose name you should know
但是还有第三个答案 这位科学家的名字你也应该知道
Get the story of the woman behind the double helix with this video
通过这个视频来了解DNA双螺旋结构背后那个女人的故事

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视频概述

DNA检测并不能完整地反映你从哪儿来

听录译者

收集自网络

翻译译者

Karasu

审核员

审核员MS

视频来源

https://www.youtube.com/watch?v=YiydsMxOdM8

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