10.Many of us remember cloned dinosaurs running wild in the film Jurassic Park.And the idea of using technology to revive extinct species has long fascinated writers,directors,and scientists.
According to The Telegraph,woolly mammoths(长毛猛玛象) may walk the earth once more,now that scientists have taken another step toward realizing a long-held dream-recreating their DNA.Mammoths became extinct around 10,000years ago.However,since the discovery of near perfect preserved remains in Arctic permafrost(北极冻土带) in May 2013,a variety of research studies have been carried out since.
Geneticists analyzed DNA from the remains,looking for genes which separated mammoths from elephants,such as hairiness and ear size.They then used the results to reproduce exact copies of 14mammoth genes."It is the first time that mammoth genes have been alive-although so far it has only been done in the lab,"Gorge Church,lead researcher of the project,told the Saturday Times.Church then used a new technique which allows scientists to edit DNA carefully,replacing sections of elephant DNA with the mammoth genes.So"we now have functioning elephant cells with mammoth DNA in them",he said.
However,Church ruled out the possibility of bringing the mammoths back to life via cloning from frozen remains.He said he"preferred to focus on rebuilding the full mammoth genome by analyzing DNA from preserved remains and putting it into the cells of its closest living relative-the Asian elephant",reported The Telegraph.Church argued that the return of the woolly mammoths-or rather,the return of something very similar-could help bring back fragile(脆弱的) ecosystems.However,some scientists believe that bringing back the mammoth would be unethical.
"What's the mess?We can be as irresponsible with the environment as we want,then we'll just clone things back?"Alex Greenwood,an expert on ancient DNA,told the Sunday Times,"Money would be better spent focusing on conserving what we do have than spending it on an animal that has been extinct for thousands of years."
32.What can we infer from the passage?C
A.Scientific studies on reviving extinct species didn't begin until May 2013.
B.The technology to revive extinct species is already mature.
C.Church and his colleagues tried to reproduce mammoth DNA.
D.Church managed to list all the genes separating mammoths from elephants.
33.According to the text,ChurchC.
A.had serious doubts about discovering the full mammoth genome.
B.aimed to clone the extinct mammoth from frozen remains on his own.
C.could help save fragile ecosystem if bringing back something similar to the mammoth.
D.believe their successful experiment could change the Asian elephant into mammoths.
34.Alex Greenwood believes thatD.
A.it is unnecessary to worry about the extinction of Asian elephants at present.
B.it's necessary to bring back species beneficial to humans from extinction.
C.the return of the woolly mammoth would help to balance ecosystems.
D.it's more important to protect present species than to bring back extinct ones.
35.What's the best title of the passage?A
A.Mammoths could return?
B.Mammoths'return helps ecosystems.
C.Mammoths have been extinct for ages.
D.Mammoths'clone from frozen remains.