B
The Royal Swedish Academy of Sciences awarded the Nobel Prize in Chemistry 2020 to two women scientists, Charpentier and Doudna, “for the development of a method for gene editing."
The discovery of these genetic scissors was unexpected.During Charpentier' s studies of Streptococcus pyogenes, one of the bacteria that cause the most harm to humans, she discovered a previously unknown molecule(分子），tracrRNA. Her work showed that tracrRNA is part of bacteria's ancient immune system, CRISPR/Cas. Charpentier published her discovery in Nature in 2011 and described how tracrRNA works with the Cas9 protein(蛋白质）to follow and kill viruses by cutting up their DNA.
Then in that same year,Charpentier began to cooperate with Doudna, an experienced biochemist in RNA.Together, they succeeded in recreating the bacteria's genetic scissors in a test tube and simplifying the scissors' molecular components so they were easier to use.They then reprogrammed the genetic scissors. In their natural form, the scissors recognize DNA from viruses,but Charpentier and Doudna proved that they could be controlled so that they can cut any DNA molecule at a predetermined site. Where the DNA is cut, it is then easy to rewrite the
code of life.
Since the CRISPR/Cas9 genetic scissors were discovered in 2012, their use has exploded though there are concerns that the technology could be misused. This tool has contributed to many important discoveries in basic research, and plant researchers have been able to develop crops that withstand mould, pests and drought. In medicine, clinical trials of new cancer therapies are underway,and the dream of being able to cure inherited diseases is about to come true.
24.According to Charpentier's studies of Streptococcus pyogenes, tracrRNA_____
A. can change life's DNA precisely
B. causes the most harm to human beings
C. is a previously unknown immune system
D.works with Cas9 protein to split viruses' DNA
25. Which order shows the discovery of the genetic scissors?
a. Charpentier began to cooperate with Doudna.
b. Charpentier published her discovery in 2011.
c.Charpentier studied Streptococcus pyogenes.
d. The bacteria's genetic scissors were recreated.
e.The genetic scissors were then reprogrammed
A.a-b-d-c-e
B.c-a-b-e-d
C.a-d-e-c-b
D.c-b-a-d-e
26.What is the last paragraph mainly about?
A. Concerns about the misuse of genetic scissors.
B.The widely-spread use of the genetic scissors.
C.The important discoveries in basic research.
D.Contributions to cure for inherited diseases.
21.Which of he following is the best title for the text?
A.Cooperation:Secret to Success in Scientific Researches
B.Genetic Scissors:a Tool for Rewriting the Code of Life
C.Charpentier & Doudna:Women Scientists Acknowledged
D.The Nobel Prize in Chemistry: a Promoter of Gene Editing
