小题1: Britain may be the most red-headed country in the world. About 1 to 2 percent of the world’s population has red hair, but in the UK the numbers are much higher, with 13 percent of Scots, 10 percent of the Irish, and 6 percent of people in England having red hair, according to the BBC. 小题2: Scientists have tried to explain why some people have red hair for some time and now they may have found an answer: the dull weather in Britain. The human body needs vitamin D from sunshine, but unfortunately people living in Britain do not have enough of it because of its maritime climate. In fact, Britain gets even more cloud than countries in the far north of Europe. In Sweden, for example, the average daily hours of sunshine is 5.4 . In Scotland it is only 3.1 hours. 小题3: To deal with this, the DNA of people living in these areas has changed slightly; scientists call this a mutation. Originally, the coloring on our body is a mixture of two kinds of melanin – black melanin is suppressed while only red / yellow melanin is made. The result is red hair, light skin color, freckles and a greater sensitivity to sunlight. 小题4: However, what’ s more interesting is that the redhead DNA mutation is recessive, which means it is hidden and can often skip generations without showing. At least 1.6 million Scots carry a redhead gene mutation, and most are unaware that they do. This is why a person who does not have red hair can still produce red-haired children if he or she is a carrier of this special DNA. 小题5: The research on red hair, like many areas of science, is contradictory(不一致). In 2002 researchers showed that redheads are more sensitive to pain, and need more anesthetic during surgery than people with blonde or dark hair. However, in 2005 scientists found that a MCRIR mutation gives redheads a higher tolerance for pain. Research into these aspects of red hair genetics continues. Redheads should though be more careful about their exposure to sunlight as they are at an increased risk of contracting skin cancer. If you are a redhead, the advice is not to stay out of the sun, but to be careful about how much exposure you get, and to cover yourself with a high factor sunscreen. |