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31.Where is this passage most likely taken from
A.A travel guide about Honolulu's attractions.
B.A cooking magazine featuring seafood recipes.
C.An investigative report on marine conservation issues.
D.An adventure novel set in Hawaii's fishing community.
D
Scientists from the University of Cambridge found a gene problem that causes PRA
(犬类进行性视网膜菱缩)in English Shepherd Dogs.They developed a DNA test to
identify this issue before dogs lose their sight.This helps the animal keepers stop the
disease from spreading to puppies (young dogs).Usually,owners don't know their dog
has PRA until it's middle-aged.By then,the dog might have already made puppies with
the bad gene.But now,PRA can be prevented quickly from English Shepherds.
Katherine Stanbury,a researcher,explained,"Once a dog starts to lose its vision.
there is no treatment;it will eventually become completely blind.But with the new DNA
test,there's no reason why any more English Shepherd Dogs should be born with this
form of PRA.It gives keepers a way to get rid of the disease entirely."
The gene for PRA is hidden.A dog needs two bad copies of the gene to get PRA.
One bad copy means the dog can pass it on.If two dogs with one bad copy have
puppies,one out of four might get PRA.Dog keepers frequently breed(繁殖；饲养)
English Shepherds from close families,which makes them more likely to have gene
problems.The study started when an owner asked for help with a blind English
Shepherd.The team collected DNA samples from other English Shepherds and used
high-tech methods to find the exact gene issue.
The university now offers a DNA testing service for dog owners to prevent inherited
diseases that are passed through genes.The test costs s 48 and is done by rubbing the
dog's mouth with special cotton.Dr.Cathryn Mellersh noted,"Owners might not notice
their dog's vision problems until the dog bumps into things.For the cost of a good bag of
dog food,owners can test their English Shepherds for PRA before they breed.This is to
prevent,not to cure.It means a lot to breeders.They no longer have to worry if their
puppies will stay healthy or develop this terrible disease.
This research could also provide insights into a similar human disease called
retinitis pigmentosa(视网膜色素变性症)，which also causes blindness.
高二·英语第5页（共10页)》

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