In February 2001 in the scientific magazine Nature, an article was published that was described by US President Bill Clinton as the most important, most wondrous map ever produced.

But what is this amazing map? It is the human genome sequence. The genome is your genetic constitution. It is the information that you inherited from your parents. This genetic information consists of 3 billion pieces of data in the form of DNA. And DNA is found in every cell of every living thing.

Background Information:

DNA

It was in 1953 that a young Englishman, Francis Crick, and an even younger American, James Watson announced that they had found “the secret of life”. They had uncovered the shape of the DNA molecule (deoxyribonucleic acid) and it was shaped like a twisted staircase, the famous double helix shape. The chemical had actually been isolated by a Swiss scientist long before, in1869, but for over fifty years no one had realized its importance to life. Crick and Watson, with another American, Oswald Avery, had earlier demonstrated that DNA was the stuff of genes: the packages of genetic information aligned along the chromosomes inside the nucleus of cells. The announcement in 2001 that the human genome had been mapped, showing the sequence of a three billion unit code, was also that “the secret of life” had been found.

Key words:

wondrous: impressive and beautiful or exciting.

genetic: the complete set of genes in a living thing.

sequence: a set of related things that happen or are arranged in a particular order.

constitution: the form or structure of something, or the way in which it is organized

inherit: to be born with the same appearance or character  as one of your parents

What does the genome do? If you imagine that your body is a complex biological machine then the genome is the blueprint for that machine. This blueprint includes the list of parts of the machine and instructions for how the pieces are put together. The instructions are called genes. Your genes give you your physical characteristics such as height, hair colour and eye colour.

But the genome is not just a list of all the genes in our body. It also shows how the genes interact in order to carry out a range of functions, such as turning an embryo into a baby, or fighting disease. So, understanding how genes fit together allows us to read the complete set of instructions for making human beings.

Key words:

Blueprint: a detailed plan for doing something new, or something that is a model for how something should be done

embryo: an animal or human before it is born, when it is beginning to develop and grow

You are 99.9% the same as the person sitting next to you and a stranger on the other side of the world. You are even closer than that to your mother, father, sister, brother, uncle, cousin or grandfather. A difference of 0.1% may seem tiny but it equals about 3 million differences at the genetic level, which is plenty to show how everyone is a unique individual. Some of the differences have no apparent effect but others influence our appearance, behaviour, how likely we are to suffer from disease and how we respond to medical drugs.

It is also clear that the old idea that skin colour is a useful way of describing the differences between people is completely false. The differences within racial groups are often greater than those between people of different colours. In other words, theories of race and racial superiority have no basis in fact at the genetic level.

 One surprising discovery of the human genome project was just how few genes we have, about 31,000. We know that a fly has 13,000 genes and a worm 17,000 genes so people had thought humans, being much more complex creatures, would have many times more genes. The answer to complexity however, is not in the sheer number of genes, but in what our genes do, compared to a fly and a worm. A further point to consider is that 99% of our genetic sequence is shared by chimpanzees — solid proof of the truth of the theory of evolution.

What are the practical benefits of knowing the sequence of the human genome? One benefit is that all biological scientists will gain more understanding of how we are made. For example, we can follow how our ancestors have moved across the world in past centuries, by tracing genetic similarities between peoples over time and space.

Key Words:

trace: to discover the origin of something or how it developed

But the most important use of the new understanding of our genetic sequence will be in medicine and will change this field greatly. By looking at our genetic make-up and how it varies between individuals we can learn why some people respond better to drug treatment than others. Doctors hope that by isolating the genes that respond to certain drugs we can pinpoint exactly what we need to do to cure a problem. The final hope, of course, is to identify possible problems such as cancer before they occur. Then we may be able to design special drugs that are effective for particular groups of patients.

This possibility of being able to intervene and stop problems before they happen has led to accusations that we are “messing with nature”. Like other great scientific advances, the sequence of the human genome can be used for good or bad purposes.

Key words:

Isolate: to separate a substance from others using a scientific process

Pinpoint: to discover or explain exactly what something is

Intervene: to become involved in a situation in order to try to stop or change it

Accusation: a claim that someone has done something illegal or wrong

Genetic testing is now available in many countries. But what happens, for example, if a mother tests her unborn child and finds it is likely to suffer from a disease in later life. Should she still give birth? If so, when should she tell the child about the disease it will suffer from later? Or should she decide not to have the baby?

On the other hand, knowing that genetically you are likely to suffer from heart disease, for example, could lead you to make better choices about how to live: by not smoking; eating healthy foods; exercising regularly; and taking certain medicines years before the first physical signs of a heart problem appear.

Another worry that some people have is that information about an individual’s genetic make-up could lead to someone with  potential problems being denied a job or refused health insurance. Many countries are trying to pass laws to make sure that an individual’s genetic information should be private.

Key words: 

potential: possible or likely in the future

Learning the sequence of human genomes is just a start on the road towards a complete understanding of what makes human beings work. It will be many years before that happens. By then, perhaps, the world will have become ready to use the knowledge wisely.

2001年2月，科学杂志《自然》发表了一篇文章，被美国总统比尔•克林顿评为“人类所绘制的最重要、最令人惊奇的地图”。       

然而，这张神奇的地图是什么呢？它就是人体基因组。基因组就是你的遗传构造。它是你继承于父母的信息。这种遗传信息由30亿个DNA数据组成。所有生物的每一个细胞中都能找到DNA。

基因组有什么功能呢？如果把你的身体想象成一台复杂的生物机器，那么基因组就是这台机器的蓝图。这幅蓝图包含了机器的零件清单和他们的组装说明。这份组装说明被称为基因。基因赋予你外表特征，如高矮、头发颜色和眼睛的颜色。

但基因组还不仅仅是我们身体里所有基因的清单。它还展示出基因如何相互作用以执行一系列的功能，如将胚胎变成婴儿，或战胜疾病。因此，了解基因是怎样组合在一起的就使我们得以读取人类构造的完整说明。

你和任何一个坐在你身旁的人，以及世界另一端的某个陌生人有99.9%的相同性。而你和你的母亲、父亲、姐妹、兄弟、舅舅/伯父、堂/表兄弟姐妹、祖父之间相同的比例就更大。0.1%的差异性可能看上去很微小，但它相当于基因层面的300万处差异，这足以显示出每个人为独特的个体。有的差异没有明显的影响，但其他的则影响到我们的外貌、举止、患病的可能性和对于药物的反应。

很明显，认为肤色能用于区别人与人之间的差异的旧观念是完全错误的。种族内部的差异往往比不同肤色人之间的差异更大。换句话说，种族优越理论在遗传层面上是毫无根据的。

人体基因组项目的一项令人吃惊的发现就是人类基因很少，大约31000个。我们知道苍蝇有13000个基因，昆虫有17000个基因，因此，人们曾以为作为比它们复杂得多的生物，人类的基因会比它们多出很多倍。然而，解答复杂性的答案不在于单纯的基因数量，而在于和苍蝇及昆虫相比我们的基因功能。另外一点值得考虑的是我们有99％的基因组和猩猩相同——这是进化论真实性的有力证据。

知道了人类基因组有什么实际的好处呢？好处之一就是生物科学家将对我们是怎样构成的有更多了解。例如，我们可通过探索不同时间和空间的人们之间的相似之处追寻在过去的世纪里我们的祖先是怎样迁移的。

但是我们对基因组所取得的新认识的最重要的运用是在医学上，它将使医学大为改观。通过审视我们的遗传构造以及遗传构造的个体差异，可以了解为什么有的人对药物治疗的反应比其他人好。医生希望通过分离对某些药物产生反应的基因，能够确定为治疗某种疾病要采取什么措施。当然，最终的希望是在病发前发现问题，如癌症。这样，我们或许可以为具体病人研制特效药。人类有能力在问题发生前对其进行干预和阻止的可能性引起了非议，有人说这是“扰乱自然”。像其他科学上的伟大进步一样，人类基因组可以用于好的目的也可以用于不好的目的。

现在很多国家都可以进行基因测试。但是，举个例子来说，如果一位母亲对她未出生的孩子进行测试发现孩子将来有可能患某种疾病时怎么办呢？她仍然应该把孩子生下来吗？如果这样，她应该什么时候告诉孩子以后将会得病呢？或者她是否应决定不要这个孩子呢？

另一方面，知道你自己有可能患病（比如说心脏病）可以让你更好地选择生活方式：不抽烟；吃健康食品；定期锻炼；在首次出现心脏问题征兆前几年就开始服用某些药品。

人们另外一个担心是，了解个人基因构成可能使有潜伏疾病的人在找工作或购买医疗保险时遭到拒绝。很多国家正尝试制定法律来保证个人遗传信息的保密。

了解人类基因组仅仅是在完全掌握人体运作奥秘的道路上迈开了第一步。要掌握它还需要很多年。也许到了那时候，世界已经具备好明智地运用这一知识的条件了。