3．
On June 26，2000，two scientists，called Francis Collins and Craig Venter，told the world that they could now read the whole"map"of the human body：DNA．DNA is something that everybody has，and it tells the body what to do．DNA is the reason that we look like our mother and father，because we get some of their DNA to make our own．
People have been trying to understand the human body for a long time．In 1860，Gregor Mendel discovered a special reason why we look the same as other people in our family．It is because of small things named "genes" in our body．In 1953，James Watson and Francis Crick made another discovery and found out that those small parts are real messages written in the DNA with a special language．
In 1961，Marshall Nirenberg and Johann Matthaei found a message in DNA showing how DNA tells the cell （細(xì)胞） to build its parts．Scientists have now found all the words in the DNA map，but we still do not understand what they all do．By understanding what just one"word"means，we can help save more people from several illnesses．
Most people hope that this will help make better medicine and help sick people．Other people worry that when people begin to know more words and find out lots of other information，we might use it in a wrong way，just to make people more attractive，or stop sick people from getting jobs．Man would have to meet a lot of trouble if DNA technic wasn't limited in use．
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51．When did we first know why we look like other people in our family？D
A．In 1860．B．In 1953．C．In 1961．D．In 2000．
52．What does the underlined word"gene"mean？C
A．The"map"of DNA．B．A special language．
C．Small parts of DNA．D．DNA．
53．What did the two scientists first discover in 1961？D
A．The"map"of DNA．B．A new illness．
C．The language of DNA． D．A message of DNA．
54．What can we do if we understand some"words"of the language inside the body？B
A．Make people get new jobs．B．Make medicine for illnesses．
C．Make maps of human．D．Make people less attractive．
55．What do people think about this work？A
A．It can cause good or bad results．B．It can cause only good results．
C．It can cause good results but won't work．D．It can cause only bad results．
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