新闻周刊:非洲基因对癌症研究很重要(2)

（单词翻译）

Unpacking¹ the Genome

解构基因组

As a Nigerian-born scientist specializing in genetics and health disparities, Rotimi foresaw the consequences of omitting Africans from genome studies years before many other researchers even noticed.

作为一名尼日利亚裔专门研究基因和健康差异的科学家，罗蒂米早在许多其他研究人员之前就预见到了将非洲人排除在基因组研究之外的后果。

And he was uniquely positioned to do something about it.

他处在一个独特的位置，可以为此做些什么。

Born in Benin, Nigeria's fourth-largest city, Rotimi first saw health inequalities in a big way in America.

罗蒂米出生在尼日利亚第四大城市贝宁，他第一次在美国看到了医疗的不平等。

He came to the U.S. for graduate school at the University of Mississippi, where many of the state's wealthiest families send their children, a trip that introduced him to his first Big Mac.

他来到美国密西西比大学读研究生，在那里，该州许多最富有的家庭都会把孩子送到那里，这趟旅行让他第一次接触到了巨无霸汉堡。

"I just couldn't eat it," he recalls.

“我就是吃不下”，他回忆道。

"I couldn't fathom⁴ the concept of bread, meat and leaves together."

“我无法理解面包、肉和菜叶混在一起的概念。”

Worse was the taste of inequality he got while traveling around the state.

最糟糕的是罗蒂米在密西西比州旅行时所感受到的不平等。

"That is when poverty speaks very loud, when you are in an environment with a lot of resources, but you don't seem to have them," he says.

“当你处在一个资源丰富的环境中，但你似乎一无所有，贫穷就会格外扎心，”他说。

He returned to Nigeria armed with a graduate degree.

他带着研究生学位回到了尼日利亚。

But after six months of job searching, he had yet to find an opportunity to do the research he knew was needed.

但经过6个月的求职，还没有找到机会做需要做的研究。

He returned to the U.S., eventually earning doctorate⁵ degrees in public health and epidemiology.

他回到了美国，最终获得了公共卫生和流行病学的博士学位。

Those years deepened his awareness⁶ of the importance of genes⁷ to health.

读博的那些年加深了他对基因影响健康的认识。

Life in Nigeria had already shown him that sickle⁸ cell disease was fated by birth, not by upbringing.

尼日利亚的生活已经告诉他，镰状细胞病是先天的，而不是后天发生。

Now, his research on hypertension among Africans around the world showed him that although lifestyle and the environment shape health, so does DNA⁹.

现在，他对世界各地非洲人高血压的研究表明，尽管生活方式和环境塑造了健康，但DNA也不可忽视。

As Rotimi was appreciating the power of genetic³ inheritance, scientists were on their way to sequencing the first human genome.

当罗蒂米正沉醉于基因遗传的力量时，科学家们正在对第一个人类基因组进行测序。

Tightly coiled inside the nucleus¹⁰ of every human cell, the genome consists of about 20,000 genes that encode proteins guiding the multitude of biological processes happening all the time in our bodies.

基因组紧紧盘绕在每个人类细胞的细胞核内，由大约2万个基因组成，这些基因编码蛋白质，指导着我们身体中每时每刻都在发生的众多生物过程。

Genes, in turn, are made of DNA, helical strands¹¹ of compounds called nucleotides that contain chemicals called bases.

反过来，基因是由DNA，即核苷酸的螺旋链组成，核苷酸含有一种叫做碱基的化学物质。

These four different bases—known most commonly by the initials A, C, T and G—are the language of the genetic code that makes up each unique individual’s blueprint¹².

这四个不同的碱基——最常见的形式是首字母A、C、T和G——是构成每个个体蓝图的遗传密码的语言。

A human genome—that is, the complete set of a person’s genes—consists of 3 billion bases.

一个人的基因组，也就是一个人的基因的完整集合，由30亿个碱基组成。

The Human Genome Project, which was completed in 2003—by then, Rotimi was teaching microbiology at Howard University, in Washington, D.C.—sequenced most of a single person's genome.

人类基因组计划于2003年完成，当时罗蒂米正在华盛顿特区的霍华德大学教微生物学——对一个人的大部分基因组进行测序。

The breakthrough wasn't so much the sequence itself but the technology.

这一突破与其说是序列本身，不如说是技术。

If research could match diseases or drug reactions to errant genes, doctors could tailor treatments around the unique genome of each patient.

如果研究能够将疾病或药物反应与出问题的基因相匹配，医生就可以针对每个病人的独特基因组量身定做治疗方案。

To arrive there, though, scientists had to study the small ways a genome varies from one person to the next.

但要实现这样的治疗，科学家们就不得不研究不同人的基因组的细微差异。

The tiny fraction of our DNA that differs, researchers thought, had to be responsible for many inherited conditions.

研究人员认为，我们DNA中微小的差异，必然影响着许多遗传疾病。

What they needed to study was not one genome but many.

他们需要研究的不是一个基因组，而是多个基因组。

They were looking for changes to single bases—a mutation¹³ from an A to a C, or a G to a T—among the 3 billion in a human genome.

他们正在人类30亿基因组中寻找单个碱基的变化——从A到C的突变，或者从G到T的突变。

These can occur when DNA replicates¹⁴, either when a baby is conceived or as cells divide during our lives.

这些可能发生在DNA复制的时候，或者是怀孕的时候，或者是在我们的生命中细胞分裂的时候。

These swaps¹⁵, called single nucleotide polymorphisms (SNPs, pronounced snips), are often harmless but sometimes alter how a gene² works, raising the risk for certain diseases.

这些突变称为单核苷酸多态性（简称SNP），通常无害，但有时会改变基因的工作方式，增加某些疾病的风险。

The wrong SNPs can render people more susceptible¹⁶ to Alzheimer’s, some blood diseases, male infertility¹⁷ and cancer, among other conditions.

错误的SNP会使人更容易患上阿尔茨海默氏症、一些血液疾病、男性不育症和癌症等疾病。

And once they're in the genome, they can be passed to the next generation.

一旦错误的SNP进入基因组，就会传给下一代。

Precision medicine is based on the idea that finding a culprit SNP can lead to treatments targeted against the gene in which that SNP sits.

精准医学是基于这样一种想法：找到罪魁祸首SNP，就可以针对SNP所在的基因进行治疗。

To find SNPs, researchers conduct association studies in which they compare whole genomes of many people.

为了发现SNP，研究人员进行了相关研究，比较了许多人的整个基因组。

After the Human Genome Project was done and the cost of sequencing genomes came down, these genome-wide association studies picked up the pace.

人类基因组计划完成后，测序基因组的成本降低了，这些全基因组关联研究加快了步伐。

But they suffered from a diversity problem: Almost none of them included African genomes.

但研究面临着一个多样性问题：几乎没有一个包括非洲基因组。

When those first few people left Africa 100,000 years ago, they took their inherited SNPs along with them.

10万年前，第一批人离开非洲时，他们带走了遗传的SNP。

But they left behind an enormous amount.

但是还留下了许多。

And the larger population that remained in Africa meant more genomes churning out variety, generation upon generation.

而留在非洲的更多的人口意味着更多的基因组，一代又一代地生产出各种各样的基因。

Because the ancestral trees of Africans have been branching out for so much longer than those of Europeans and Americans, they contain much more variation.

由于非洲人的祖先树比欧洲人和美国人的分支要长得多，所有产生了更多的变异。

In fact, African genomes are the most diverse of any on the planet.

事实上，非洲的基因组是地球上最多样化的。

"We compared European and Asian populations to each other," says Sarah Tishkoff, a geneticist at the University of Pennsylvania,

“我们对比了欧洲和亚洲的人口，” 宾夕法尼亚大学的遗传学家莎拉·蒂什科夫说，

"and they were more similar than any two African populations we looked at."

“他们比我们观察的任何两个非洲人都更相似。”

When it comes to genetic diversity, Africa has a 100,000-year head start.

在基因多样性方面，非洲领先10万年。