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Genome microbiome 인간 유전체 프로젝트(the human genome project) 서범구 이엠생명과학연구원
2013-09-30 16:39:00

인간 유전체 프로젝트(the human genome project)

 

?인간 유전체 프로젝트 재조합 DNA 기술 분야에서 인류 역사에 남을 만한 거대 프로젝트로 인간 유전체 프로젝트를 꼽을 수 있다.

 

입자물리와 우주 탐사 분야에서는 큰 돈이 들어가는 거대 프로젝트가 있어왔지만, 생명과학분야에서는 인간 유전체 프로젝트가 거대 프로젝트가 되었다.

 

1990년 10월에 시작되어 2003년에 결과가 발표되기까지 13년에 걸쳐 여러 나라의 연구팀이 참여한 연구사업으로 인간의 유전체를 이루는 약 30억 염기쌍의 서열을 밝히는 것이 가장 큰 목표였다.

 

이 프로젝트를 통하여 인간 자신의 유전 설계도를 처음으로 우리 자신이 보는 상황이 되었다.

 

이 연구 수행에서 몇 가지 놀라운 결과가 드러났다.

 

전체의 98%가 소위 졍크 DNA (쓰레기 DNA)라고 부르는 것으로 현재 인간에서 직접적으로 어떤 기능을 하는 유전자 산물을 만들지 않는 DNA라는 점이다.

 

즉, 2% 만이 단백질 또는 RNA 산물을 만들어내는 유전자이며, 이것과 연관된 결과인데 우리 유전체에는 유전자가 2만 5천개 정도일 것이라는 점이다.

 

인간 유전체 프로젝트의 결과가 나오기 전에 이미 여러 생물들의 유전체 염기서열이 발표되었고 인간보다 훨씬 단순하게 생각되는 생물체들의 유전자 수가 2만 개 정도인 것이 있었기 때문에 사람의 유전자는 아마 10만 개 이상은 되지 않을까하는 예상이 많았다.

 

결과는 예상보다 훨씬 작은 숫자였다. 인간이라는 복잡한 생물기계를 만드는데 부품의 종류가 25,000개 정도라는 것인데, 쪼그만 초파리가 14,000개 정도의 유전자를 가지고 있고 선충도 19,000개 정도의 유전자를 가지고 있다는 것에 비하면 인간의 유전자는 너무 작은 것이다.

 

우리 인간이 대단한 것 같지만, 사실 생물학적으로 파리나 선충보다도 크게 부품 수가 많지 않은 기계라는 것은 당황스러운 결과였다.

 

아직도 인간의 복잡성이 어디에서 나오는지는 완전히 이해되지 않은 문제이며 앞으로도 지속적인 연구가 필요한 분야이다.

 

Ten years ago the Human Genome Project

 

Ten years ago the Human Genome Project announced it had completed the first draft of the blueprint for human life. It was hailed as a huge scientific advance, comparable to putting a man on the moon. President Bill Clinton declared: "We'll go from knowing almost nothing about how our genes work to enlisting genes in the struggle to prevent and cure illness. This will be the scientific breakthrough of the century, perhaps of all time."

The project at last laid bare the entire human genetic code – 22,000 or so genes (the precise number is still uncertain) – that make us into the people we are. Several decades of research into the cause of diseases before the project had firmly identified genes as a significant cause of many important diseases.

The first haul of genetic diseases was of those fairly rare but devastating inherited diseases, such as cystic fibrosis, that are caused by single genes. Most of the genes responsible for those had been fished out of the genome long before the sequencing project hauled in its net. But the project was expected to find genes for various far more common conditions, such as cancer, diabetes, heart disease, autism, depression and schizophrenia, because most of these conditions tend to run in families. Studies of families in which these diseases were common, particularly of twins, had established a level of heritability for each condition, and the levels were high. Autism comes out at a whopping 90%, indicating that most autism is caused by faulty genes (and certainly not by faulty vaccines). The heritability of schizophrenia was about 80% whereas conditions such as heart disease, diabetes and cancer came in anywhere between 30% and 70%.

And it wasn't just diseases that were caused by genes. Many behavioural studies indicated that intelligence, personality, sexual orientation and even voting preference seemed to be highly heritable. If genes were so powerful, it should be straightforward to identify the culprits in the genome.

But a decade later these expectations have not been fulfilled. The project that promised so much has, so far, delivered very little. Very few genes have been found that account for more than 1% of the risk of any of those common diseases. And even the most significant intelligence gene yet found is responsible for variation in individual intelligence equivalent to less than one IQ point. The scientists who went in search of whoppers netted only a host of minnows. Where are the missing genes?

Like most things in life, it turns out that genes are more complex than we thought. Those genes responsible for single-gene defects such as cystic fibrosis and haemophilia are the low-hanging fruit. Common diseases, and such attributes as intelligence, are not caused by single genes or even handfuls of genes, but probably by networks of hundreds or even thousands of genes.

To understand these networks, we need to look, not at the branches, but at the roots of the genetic tree. Genes form tangles of interactions with each other such that the effect of chopping one or another is unpredictable and depends on the connectivity of the whole network. Finding a gene responsible for a disease is mostly like finding a root responsible for maintaining a tree.

The task of unravelling the roots of biology is the new science of systems biology, in which biologists work with mathematicians and computer scientists to build models of complex networks. This is where the causes of heart disease, diabetes and autism are now being sought. To paraphrase Winston Churchill, the genome project was not the end. It was not even the beginning of the end. But it was, perhaps, the end of the beginning in the search for our genes.

 

출처

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[이 게시물은 이엠생명과학연구원님에 의해 2012-06-23 06:08:41 Microorganism에서 이동 됨]




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