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2017年12月全国大学英语四六级考试已进入备考冲刺阶段——【点击查看各科目练习汇总】。英语六级考试中六级阅读所占比重为百分之三十五，阅读训练的重要性不言而喻，然而阅读技巧也是一门学问。来看看文都四六级小编为各位整理的2017年12月英语六级阅读训练(282)——生物科技，请考生及时练习！
【文都名师】文都名师刘一男、何凯文6月四六级考前实力冲刺
【口试真题】2016-2017年大学英语四级口语考试真题及解析
【口试真题】2016-2017年大学英语六级口语考试真题及解析
【口试考点】2017年11月各地英语四六级口语考试考点汇总
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If you go down to the woods today, you may meet high-tech trees genetically modified to speed their growthor improve the quality of their wood. Genetically-engineered food crops have become increasingly common, albeit controversial. over the past ten years. But genetic engineering of trees has lagged behind.
Part of the reason is technical. Understanding. and then altering, the genes of a big pine tree are more complex than creating a better tomato. While tomatoes sprout happily, and rapidly, in the laboratory, growing a whole tree from a single, genetically altered cell in a test tube is a tricky process that takes years, not months. Moreover. little is known about tree genes. Some trees, such as pine trees. have a lot of DNA-roughly ten times as much as human. And, whereas the Human Genome Project is more than half-way throughits task of isolating and sequencing the estimated 100,00 genes in human cells. similar efforts to analyzetree genes are still just saplings (幼苗).
Given the large number of tree genes and the little that is known about them, tree engineers are starting with a search for genetic "markers". The first step is to isolate DNA from trees with desirable propertiessuch as insect resistance. The next step is to find stretches of DNA that show the presence of a particular gene. Then, when you mate two trees with different desirable properties, it is simple to check which offspring contain them all by looking for the genetic markers. Henry Amerson, at North Carolina State University, is using genetic markers to breed fungal resistance into southern pines. Billions of these are grown across America for pulp and paper, and outbreaks of disease are expensive. But not all individual trees are susceptible. Dr. Amerson’s group has found markers that distinguish fungus-resistant stock from disease-prone trees.Using traditional breeding techniques, they are introducing the resistance genes into pines on test sites in America.
Using generic markers speeds up old-fashioned breeding methods becauseyou no longer have to wait for the tree to grow up to see if it has the desiredtraits. But it is more a sophisticated form of selective breeding. Now. however.interest in genetic tinkering (基因修补) is also gaining ground. To this end, Dr.Amerson and his colleagues are taking part in the Pine Gene Discovery Project. an initiative to identify and sequence the 50,000-odd genes in the pine tree's genome. Knowing which gene does what should make it easier to know what to alter.
1. Compared with genetic engineering of food crops, genetic engineering of trees____________________.
A) began much later
B) has developed more slowly
C) is less useful
D) was less controversial
2. What does the author think about the genetic engineering of pine trees?
A) Time-consuming.
B) Worthwhile.
C) Significant.
D) Technically impossible.
3. What can we learn about the research on tree genes?
A) The research methods are the same as the analysis of human genes.
B) The findings are expected to be as fruitful as the analysis of human genes.
C) It will take as much time and effort as the analyst, of human genes.
D) The research has been mainly concentrated on the genes of young trees.
4. It is discovered by Henry Amerson’s team that_______________.
A) southern pines cannot resist fungus
B) all southern pines are not susceptible
C) the genetic marker in southern pines was the easiest to identify
D) fungus-resistant genes came originally from outside the U.S.A.
5. What is the primary objective of carrying out the Pine Gene Discovery Project?
A) To speed up old-Fashioned breeding methods.
B) To identify all the genes in the pine tree's genome.
C) To find out what desired traits the pine trees have.
D) To make it easier to know which gene needs altering.
【参考答案】
1-5 BBABB
以上就是文都四六级小编为各位考生整理的关于2017年12月英语六级阅读训练，小编希望大家能顺利的取得好成绩~
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发表于 2017-11-7 19:16:03