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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.
56.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
57.lt 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
58.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
59.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. th ey have fewer activities outside
D.they pay much attention to protecting their skin
60.The writer's attitude towarcls the discovery is .
A.neutral B.negative C.indifferent D.positive
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The Coalition for the Homeless is an organization that seeks to address the needs of the homeless population in the United States. It is a network of offices, some of which provide food and houses for the homeless population, and some of which fight for the passing of laws that would give every American the right to a place to call home. According to the Coalition’s studies, of over two hundred million people living in th U?ited States, up to three million are homeless—and the number is still growing. Since the late 1970s, fast-rising house prices, large cuts in government supported housing programs, and economic recession(经济衰退) have made it impossible for many Americans to meet housing costs. Sadly, this has resulted in a number of persons being forced to leave their homes and/or unable to find new affordable homes.According to another research, families with children appear to be the fastest-growing part of the homeless population, making up 39% of it. The old idea of a homeless person, that of the single man who gets drunk all the time, is no longer true. A much larger part of the population now finds itself homeless. Even worse, once a person becomes homeless, he often finds it impossible to find a job, since most employers require anyone who wants a job from them to provide a home address on a job application.
1. The word “address” in the first line probably means .
A. talk about B. deal with C. fight for D. write to
2. How many people are homeless in the U.S. according to the Coalition studies?
A. 39% of the population. B. 200 million people.
C. About 3 million people. D. About one-fifth of the population.
3. Homeless people often have difficulty finding a job because________.
A. they have no home addresses
B. they mostly have a drinking problem
C. they aren't supported by government programs
D. they often don't have enough work experience
4. What is the main cause of the rising number of the homeless in the U.S.?
A. The passing of new housing laws.
B. The fast growth of family size.
C. The slow construction of houses.
D. The ever-rising price of housing.
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extinction if impact of climate change and extreme weather on their homes is not handled, a UN report
showed on Sunday.
Released during the course of global climate negotiations in Durban, the report by the United Nations
Food and Agriculture Organisation (UNFAO) shows how higher temperatures, the rise in sea levels,
deforestation and overuse of land have damaged the habitats of certain species, especially in Africa.
"Many ecosystems have already been affected by increasing population, historical and recent
deforestation, short-lasting management practices and even invasive species," Eduardo Rojas, assistant
director general at the UNFAO's forestry department, said at the release of the report.
The most affected areas include mountains, islands and coastal areas, which limit the possibilities for
animals to move elsewhere and create new habitats. "The remaining populations are limited to very small
ecosystems. They have inbreeding (近亲繁殖) problems.., and at the end these species may disappear,"
he added.
Other examples of affected animals include elephants in Mall, lions in Serengeti and crocodiles in
Malawi. The report says about 20~30 percent of plant and animal species will be at higher risk of
extinction due to global warming and a significant number of local species may disappear by 2050 as a
consequence. Other consequences could include the spread of invasive species and infectious diseases,
it said.
The report urges more focus on restoration of damaged ecosystems, especially those key to dealing
with climate change such as inland waters, forests and grasslands. The UNFAO also called for the
creation of movement channels for animals in areas where their movement was affected. The organization
said while more resources (资源) were flowing to biodiversity conservation, more action at th
government and policy level was needed. It also urges local communities to develop projects that ease
the effect of climate change on wildlife, naming ecotourism activities as an example.
B. The subject of research done by Eduardo Rojas.
C. Harmful effects of damage done to ecosystems.
D. Causes of damage done to ecosystems.
B. They have difficulty finding enough food for survival.
C. They have little chance of moving to other places.
D. They can hardly find mates to produce their young.
EXCEPT ______.
B. limiting world population growth
C. creating movement channels for animals
D. urging governments and local communities to take action
B. Human activities and the animal kingdom
C. Gorillas, tigers at risk due to climate change
D. How to balance human development and animal rights
The Coalition for the Homeless is an organization that seeks to address the needs of the homeless population
in the United States. It is a network of offices, some of which provide food and houses for the homeless
population. and some of which fight for the passing of laws that would give every American the right to a place
to call home. According to the Coalition's studies, of over two hundred million people living in th U?ited States,
up to three million are homeless and the number is still growing since the late 1970s, fast rising house prices,
large cuts in government supported housing programs, and economic recession have made it impossible for
many Americans to meet housing costs. Sadly, this has resulted in a number of persons being forced to leave
their homes and or unable to find new affordable homes. According to another research, families with children
appear to be the fastest-growing part of the homeless population, making up 39% of it. The old idea of a
homeless person, that of the single man who gets drunk all the time, is no longer true. A much larger part of
the population now finds itself homeless. Even worse, once a person becomes homeless, he often finds it
impossible to find a job, since most employers require anyone who wants a job from them to provide a home
address on a job application.
B. deal with
C. fight for
D. write to
A. 39% of the population.
B. 200 million people.
C. About 3 million people.
D. About one-fifth of the population.
B. they mostly have a drinking problem
C. they aren't supported by government programs
D. they often don't have enough work experience
B. The fast growth of family size.
C. The slow construction of houses.
D. The ever-rising price of housing.