| 阅读理解。 |
| Can people change their skin color without suffering like pop king Michael Jackson? Perhaps yes. Scientists have found the gene that determines skin color. The gene comes in two versions, one of which is found in 99 per cent of Europeans.The other is found in 93 t0 100 per cent of Africans, researchers at Pennsylvania State University report in the latest issue of Science. Scientists have changed the color of a dark - striped zebrafish (斑马鱼) to uniform gold by inserting a version of the pigment (色素) gene into a young fish.As with humans, zebrafish skin color is deter-mined by pigment cells,which contain melanin (黑色素).The number, size and darkness of melanin perpigment cell determine skin color. It appears that, like the golden zebrafish, light - skinned Europeans also have a mutation (变异) in the gene for melanin production.This results in less pigrnented skin. However, Keith Cheng, leader of the research team, points out that the mutation is different in hu-man ancl zebrafish genes. Humans acquired dark skin in Africa about l.5 million years ago to protect bodies from ultra - violetrays of the sun. which can cause skin cancer. But when modem humans leave Africa to live in northem latitudes, they need more sunlight on their skin to produce vitamin D. So the related gene changes, according to Cheng. Asians have the same version of the gene as Africans, so they probably acquired their light skin through the action of some other gene that affects skin color, said Cheng. The new discovery could lead to medical treatments for skin cancer.lt also could lead to research in-to ways to change skin color without damaging it like chemical treatment did on Michael Jackson. |
| 1. Scientists have done an experiment on a dark -striped zebrafish in order to |
| A. fincl the different genes o humans' B. prove the humans' skin color is determined by the pigment gene C. find out the reason why the Africans' skin color is dark D. fincl out the ways of changing people's skin color |
| 2. It can be inferred from the passage that . |
| A. nowadays people who want to change their skin color have to suffer 8 lot from the damage caused by the chemical treatment B. Europeans and Africans have the same gene C. the new discovery could help to find medical treatments for skin cancer D. there are two kinds of genes |
| 3.The passage mainly tells us that . |
| A. scientists have found out that people's skin color is determined by the gene B. the new discovery could lead to research into ways to change skin color safely C. pop king Michael Jackson often changed his skin color as he liked D. people can not change their skin color without any pain |
| 4. The reason why Europeans are light - skinned is probably that . |
| A. they are bom light - skinned people B. light - skinned Europeans have mutation in the gene for melanin production C. they have fewer activities outside D. they pay much attention to protecting their skin |
| 5. The writer's attitude towarcls the discovery is . |
| A. neutral B. negative C. indifferent D. positive |