题目内容：

    Studying the DNA of 300 mice has flagged up genes which have been linked to hereditary (遗传的) sight loss for the first time. Researchers say because mice’s genes are so similar to humans’, their findings could lead to the treatment of more genetic diseases.

Scientists at the University of California, Davis studied information from a data bank of mice’s genetic material. They found 347 genes linked to eye problems, with just 86 of them having been studied in the past.

Only around 50 to 75 percent of hereditary eye diseases in human can be explained with present science. The researchers believe these hundreds of new genes found in mice could be a key to explaining-and therefore being able to treat the other 25-50 percent.

“This is extremely valuable for people with hereditary eye disease,” said researcher Professor Ala Moshiri. “All researchers are going to start using these data. In the past, we knew the problem was there but we didn’t know where to look. Now eye centers can call back patients and screen them for these new genes. We expected that more and more of these genetic diseases will be treatable.” Also, the fact is that more than 60 percent of eye problems at birth are ones resulting from the baby’s parents!

Thanks to data from the International Mouse Phenotyping Consortium (IMPC), which is trying to work out what every single gene in a mouse is responsible for, with the aim of translating it to humans, scientists are moving closer to figuring out all genetic causes of blindness. To do this, scientists separate a single gene from other ones at a time and then observe what effect it has on the mouse for a long time. This has so far been done more than 7,000 times and has achieved great success. Researchers are now working alongside eye care centers in Texas and Iowa in order to compare the mice’s genes to those of patients.

1.How many hereditary-sight-loss-related genes were newly found?

A. 86. B. 261.

C. 300. D. 347.

2.Why is the percentage of genetic eye problems mentioned in paragraph 3?

A. To show the significance of studying mice’s genes.

B. To prove mice’s genes are similar to humans’.

C. To warn the high risk level of suffering them.

D. To explain how common they are among people.

3.What should scientists do first to unlock secrets of genetic blindness?

A. Compare humans’ genes with mice’s.

B. Recognize each gene’s role of humans.

C. Set apart a gene of a mouse each time.

D. Figure out each gene’s function of a mouse.

4.What can be a suitable title for the text?

A. New Ways to Cure Sight Loss

B. Genes Found Behind Eye Problems

C. Genetic Diseases Discovered in Mice

D. Humans Genes Causing Eye Diseases