In Terry Gilliam's 1985 film “Brazil,” a tiny printing error in a bureaucratic document leads to the mistaken arrest and detention of an innocent man. A single letter is changed in a file and the set of instructions are automatically followed by the authorities. In some ways, this is analogous to the way the machinery of our cells reads the instructions contained in our DNA. Here, too, a single change can have unexpectedly far-reaching consequences but unlike the Orwellian machinery depicted in “Brazil,” changes to the DNA code are not always for the worse. A good example of this was in a paper published this week in the journal Current Biology. It concerns a gene called MMP3, which makes a protein that affects the elasticity and thickness of blood vessels. More specifically, the researchers were looking at a length of DNA that determines how much of the blood-vessel protein is produced. This regulatory part of the gene is 1,600 genetic units, or nucleotides, in length. If each nucleotide is thought of as a word on a page, that's equivalent to text about twice the length of this article. Researchers found that a change of just one nucleotide in the regulatory sequence―one word in a story twice this long―is enough to retard the progress of coronary-artery heart disease. coronary-artery (冠動脈) ややこしいから、ここで説明 まず、遺伝子に重要なものとして、A(アデニン)C(シトシン)G（グアニン)T(チミン)U（ウラシル）の塩基があります。例えば、アデニンの化学式はC5H5N5です。これら塩基に糖そして、リン酸基が結合したのが、ヌクレオチドです。上の段落を説明すると、 ①ヌクレオチド1600個で、MMP3遺伝子中のregulatory partを構成する。 ②ヌクレオチド（が持つ情報量）を１ページ中の一つの単語とすると、that (regulatory part＝1600個)はこの記事の２倍の長さに相当する。 ということは、この記事の語数は1600語ということです。このうち、たった一文字変化するだけで、冠状動脈の進行を遅らせる、とあります。遺伝子の持つ情報がいかに細かいかわかりますよね。
What's surprising about this is that the change in the gene doesn't affect the shape of the protein itself, which is what geneticists usually mean when they refer to gene “mutations.” In this case, the tiny change only influences how much of the protein is produced. There are many factors that influence the risk of heart disease, and this is one of the more subtle. Heart disease is the leading cause of death in Europe, with Britain having one of the worst records. For example, in 1998, 150 out of every 100,000 adult males in the population died of heart disease. Japan, by contrast, has the lowest level of heart disease in the world, with only 17 men per 100,000 succumbing. The differences are largely due to environmental factors, mainly diet. The average Japanese diet contains far less saturated fat than the British one. I say “average” because in Okinawa, for example― which has 44 branches of McDonald's and was the first prefecture in Japan to welcome the American fast-food chain―47 percent of men aged 20-60 are classified as obese. Despite the poor health record in Britain, though, the new research findings on MMP3 show that heart disease would have had a much greater death toll but for natural selection in the relatively recent past.