Can people change their skin colour without suffering like pop king Michael Jackson? Perhaps yes. Scientists have found the gene that determines skin colour. The gene comes in two versions, one of which is found in 99 per cent of Europeans. The other is found in 93 to 100 per cent of Africans, researchers at Pennsylvania State University report in the latest issue of Science.
Scientists have changed the colour of a dark-striped zebra fish to uniform gold by inserting a version of the pigment (色素) gene into a young fish. As with humans, zebra fish skin colour is determined by pigment cells, which contain melanosomes (黑色素体). The number, size and darkness of melanosomes per pigment cell determines skin colour.
It appears that, like the golden zebra fish, light-skinned Europeans also have a mutation (突变)in the gene for melanosome production. This results in less pigmented skin. However, Keith Cheng, leader of the research team, points out that the mutation is different in human and zebra fish genes.
Humans acquired dark skin in Africa about 1.5 million years ago to protect bodies from ultra-violet rays of the sun, which can cause skin cancer. But when modern humans leave Africa to live in northern 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 colours, said Cheng.
The new discovery could lead to medical treatments for skin cancer. It also could lead to research into ways to change skin colour without damaging it like chemical treatment done on Michael Jackson.
1.According to the passage, scientists have found .
A. people living in northern latitudes need more sunlight
B. the reason why people change their skin colour
C. the reason why people get skin cancer
D. the gene that determines skin colour
2.We can infer from the passage that .
A. people like to change their skin colour
B. a mutation in the gene for melanosome production is different in human and zebra fish gene
C. people will be able to change their skin colour without chemical treatment in the future
D. skin cancer can be cured now
3.Which of the following is NOT mentioned according to the passage?
A. The version of the pigment gene of Asians and that of Africans are the same.
B. Scientists have succeeded in turning the colour of a dark-striped zebra fish into uniform gold.
C. Dark skin can protect bodies from utral-violet rays of the sun.
D. People like pop king Michael Jackson.
4.The passage is probably taken from __________.
A. a novel B. a science report
C. a story book D. a science fiction
When I was a child, my parents taught me the difference between good and bad behavior by showing me specific examples. My mother told me that you don’t 36 other kids because you would not like 37 if they hit you. That makes 38 . But, if my mother told me to be “nice” to someone, it was too vague for me to 39 . But if she said that being nice 40 delivering daffodils to a next door neighbor, that I could understand.
I believe that doing practical things can 41 the world a better place. When I was in my twenties I thought a lot about the meaning of life. At the time, I was getting started in my 42 of designing more humane facilities for animals at big farms and slaughterhouses(屠宰场). Many people would think that to even work at a slauterhouse would be inhumane, but they 43 that every human and animal 44 dies. In my mind, I had a(n) 45 of a way to make tht dying as 46 as possible.
Back in the 1970s, I went to fifty different feedlots and big farms in Arizona and Texas and 47 them work cattle. I cataloged the parts of each facility that 48 effectively. I took the best loading ramps, and other components and 49 them into an ideal new system. I get great 50 when a farmer tells me that my corral (畜栏) 51 helps cattle move through it quietly and 52 . When cattle stay calm, it means they are not scared. And that makes me feel I’ve 53 something important.
Some people might think if I could snap my 54 I’d choose to be “normal”. But, I wouldn’t want to give up my 55 to see in beautiful, precise pictures. I believe in them.
1.A. knock B. hit C. beat D. strike
2.A. this B. which C. it D. that
3.A. sense B. difference C. sail D. way
4.A. recognize B. realize C. know D. understand
5.A. meant B. minded C. missed D. admitted
6.A. give B. turn C. make D. take
7.A. job B. career C. trade D. industry
8.A. regret B. remember C. forgive D. forget
9.A. constantly B. eventually C. immediately D. directly
10.A. description B. scene C. picture D. image
11.A. peaceful B. calm C. quiet D.silent
12.A. required B. asked C. promised D. helped
13.A. solved B. worked C. acted D. conducted
14.A. collected B. gathered C. assembled D. met
15.A. satisfaction B. expectation C. explanation D. presentation
16.A. aim B. intention C. plan D. design
17.A. hardly B. difficultly C. easily D. happily
18.A. reached B. accomplished C. adapted D. polished
19.A. fingers B. hands C. arms D. feet
20.A. skill B. possibility C. talent D. ability
It was only a very short time _______ the young lady found her cellphone stolen as she got on the crowed bus.
A. before B. when C. since D. after
When television was first introduced, the extent _______ it would affect society could not have been foreseen.
A. of which B. of what C. to which D. in which
He thought the jar made ______ earth ______ little value and let me have it ______ only 5 dollars.
A. of; of; for B. from; of; by C. from; with; for D. of; of; by
--- I recommend you first give up smoking, and then try to find a job so that you’ll start a new life.
--- _______.
A. Not in the least B. Easier said than done
C. It’s up to you D. That all depends
