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 zebrafish to uniform gold by inserting a version of the pigment(色素) gene into a young fish. As with humans, zebrafish skin colour is determined by pigment cells, which contain melanosomes(黑色素). The number, size and darkness of melanosomes per pigment cell determines skin colour.

It appears that, like the golden zebrafish, light-skinned Europeans also have a mutation(变异) 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 zebrafish genes.

Humans acquired dark skin in Africa about 1.5 million years ago to protect bodies from ultra-violet rays of the sun(太阳光紫外线), 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 colour, 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 did on Michael Jackson.

The passage mainly tells us that ________.

  A. people can not change their skin colour without any pain

  B. the new discovery could lead to search into ways to change skin colour safely

  C. pop king Michael Jackson often changed his skin colour as he liked

  D. scientists have found out that people’s skin colour is determined by the gene

It can be inferred from the passage that ________.

  A. nowadays people who want to change their skin colour have to suffer a 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

Scientists have done an experiment on a dark-striped zebra fish in order to ________.

  A. find the different genes of humans’

  B. prove the humans’ skin colour is determined by the pigment gene

  C. find out the reason why the Africans’ skin colour is dark

  D. find out the ways of changing peopl’s skin colour

The writer’s attitude towards the discovery is ________.

  A. neutral                      B. negative                   C. positive                    D. indifferent

This dictionary tells you about English words and how to use them in reading, writing and speaking English. It not only gives the meaning of words, it can also help you with spelling, word-building, grammar and pronunciation.
To use your dictionary correctly, you need to understand how the dictionary works. At the front of the book, you will find some exercises to help you make the most use of your dictionary.
If you look up the word “colour”, you will find two spellings for this word. “Colour” is used in British English, while “color” is used in American English. When there are differences between British and American spelling, the dictionary shows it with the word “BrE” for British English and “AmE” for American English.
The dictionary also helps you pronounce words correctly. We use a special alphabet (特殊字母) to show pronunciation. If you turn to the inside back face, you will see all the phonetic letters (音标) with some words to show you how they are pronounced. Just look at the inside back cover when you’re not sure how to say a word.
The most important reason for using a dictionary is to find out the meaning of a word—its definition
In this dictionary, the definitions have been written using only 2000 words. This means that the definitions of even the most difficult words are simply explained and easy to understand.
When a word has more than one meaning, read all the meanings until you find the one that correctly tells the use of the word you are looking for.
Most of the words in this dictionary can be used by people in all parts of the world.
【小题1】The AmE spelling of the Chinese word “颜色” in this dictionary is ________.

A.colour B.colarC.colorD.corner
【小题2】The phonetic alphabet help you ________ each word correctly.
A.understand B.writeC.sayD.know
【小题3】The underlined word ‘definition’ means__________
A.词性B.词条C.词义D.词库
【小题4】The dictionary explains ________.
A.some of the difficult words
B.all the words in the dictionary in a simple way
C.all easy words
D.the words with two meanings

This dictionary tells you about English words and how to use them in reading, writing and speaking English. It not only gives the meaning of words, it can also help you with spelling, word-building, grammar and pronunciation.

To use your dictionary correctly, you need to understand how the dictionary works. At the front of the book, you will find some exercises to help you make the most use of your dictionary.

If you look up the word “colour”, you will find two spellings for this word. “Colour” is used in British English, while “color” is used in American English. When there are differences between British and American spelling, the dictionary shows it with the word “BrE” for British English and “AmE” for American English.

The dictionary also helps you pronounce words correctly. We use a special alphabet (特殊字母) to show pronunciation. If you turn to the inside back face, you will see all the phonetic letters (音标) with some words to show you how they are pronounced. Just look at the inside back cover when you’re not sure how to say a word.

The most important reason for using a dictionary is to find out the meaning of a word—its definition

In this dictionary, the definitions have been written using only 2000 words. This means that the definitions of even the most difficult words are simply explained and easy to understand.

When a word has more than one meaning, read all the meanings until you find the one that correctly tells the use of the word you are looking for.

Most of the words in this dictionary can be used by people in all parts of the world.

1.The AmE spelling of the Chinese word “颜色” in this dictionary is ________.

A.colour            B.colar             C.color             D.corner

2.The phonetic alphabet help you ________ each word correctly.

A.understand        B.write             C.say              D.know

3.The underlined word ‘definition’ means__________

A.词性             B.词条             C.词义             D.词库

4.The dictionary explains ________.

A.some of the difficult words

B.all the words in the dictionary in a simple way

C.all easy words

D.the words with two meanings

 

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