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2018專八閱讀理解練習(xí)題《生物知識》
盡管現(xiàn)在離2018的專八考試還比較遙遠(yuǎn)，但是不少的考生已經(jīng)在備考2018年的專八考試了。下面，小編就為考生送上一篇2018專八閱讀理解練習(xí)題。
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. Understandng. 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 (基因修補) 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.
答案：
1.相較于糧食作物的基因工程，樹木的基因工程______________。
A)開始得較晚
B)發(fā)展得較慢
C)用處較小
D)爭議性較低
[B]本文并沒有提到樹木基因改良技術(shù)從什么時候開始，所以有可能樹木的基因改良技術(shù)和別的基因改良技術(shù)在開始的時間上相差不大，但在所取得的成果方面卻有很大的差別，因此，本題關(guān)鍵在于理解首段末句中的lag behind指的是程度上的落后，而非時間上的落后，故B正確。
2.作者對于松樹基因工程怎么看?
A)耗時。
B)十分值得。
C)很重要。
D)技術(shù)上不可能。
[B]第2段第3句中的that takes years表明研究樹木的基因改造技術(shù)將花費很長時間，因此選項A為本題答案。原文沒有就選項B和C兩方面做出討論，因此不能推斷出這兩個選項;雖然第2段首句提到technical一詞，但文章表明樹木基因改造技術(shù)是可行的。只是會花費較多的時問，因此選項D也不正確。
3.對于樹木基因進(jìn)行的研究，我們了解到什么?
A)研究方法與分析人類基因時相同。
B)人們預(yù)計研究成果會與人類基因分析一樣碩果累累。
C)所花的時間和精力與人類基因分析一樣多。
D)研究主要關(guān)注在小樹的基因上面。
[A]第2段末句中的similar cfforts指的就是task of isolating and sequencing，即分析基因的常用方法。該句表明人類基因和樹種基因的分析方法相同，但進(jìn)展有差別，因此選項A為正確的推斷。
4.Henry Amerson的研究小組發(fā)現(xiàn)，__________________。
A)南部黃松不能抵抗真菌
B)并不是所有的南部黃松都很容易染病
C)南部黃松的基因標(biāo)記最容易識別
D)有真菌抵抗能力基因源自國外而非美國
[B]選項B是一個半否定的句式，因此本題關(guān)鍵在于理解選項B的Al1...are not...結(jié)構(gòu)在意義上等同于第3段倒數(shù)第3句的not all... are...。第3段倒數(shù)第2句中的fungus-resistant stock指的是南方松樹中能抗真菌的樹種，并非別的與南方松樹毫不相關(guān)的樹種，因此A的說法不正確。
5.開展“松樹基因發(fā)現(xiàn)項目”的主要目的是什么?
A)加快舊式的育種方法。
B)識別松樹基因組中的所有基因。
C)找到松樹所具有的優(yōu)質(zhì)特點。
D)讓發(fā)現(xiàn)什么基因需要做改變的過程變得更加簡單。
[B]末段倒數(shù)第2句中的an initiative...是the Pine Gene Discovery Project的同位語，表明開展該計劃的目的，因此選項B為本題答案。其他選項都是在完成該計劃后能夠達(dá)成的工作，它們都要以松樹基因的排列組合為基礎(chǔ)，因此，這些選項都不是primary objective，而是在實現(xiàn)了primary objective之后繼續(xù)進(jìn)行的工作。
附：2018專八閱讀技巧推薦
略讀
略讀(skimming)是常用的閱讀方法之一，其主要特征是選擇性地閱讀。通常的閱讀要求看到每一個詞，每次注目看1-2個詞。略讀不需要看到每一個詞，眼睛跳動的頻率和幅度都有較大的提高，有時甚至從上一行跳到下一行。略讀不可能使你對所讀內(nèi)容全部了解，但是你能大大地提高閱讀速度，也能獲得大量的信息。
略讀的主要作用是了解文章的大意。經(jīng)過略讀之后，你對所讀內(nèi)容已經(jīng)有了大致的了解，再仔細(xì)閱讀，這時你的印象會更深刻，理解更透徹。
大部分讀者不需要正規(guī)的訓(xùn)練和指導(dǎo)就可以進(jìn)行略讀。但是有意識地訓(xùn)練會大大地提高。你的略讀速度和效率。進(jìn)行略讀訓(xùn)練的最簡單的方法是強迫自己在規(guī)定的時間內(nèi)讀完某一篇文章，開始訓(xùn)練時，可以把略讀速度定為平常閱讀的5/4倍，以后逐步提高。略讀的關(guān)鍵是增加眼跳的幅度，高度集中注意力，努力捕捉那些能引起注意或者你認(rèn)為重要的內(nèi)容。
掃讀
掃讀(scanning)是以最快的速度掃視所讀材料，在找到所需信息時才仔細(xì)閱讀該項內(nèi)容。如查找某個人名、地名、時間、地點等，也即在尋找特定信息、尋找具體事實、尋找答題所需內(nèi)容時都用這種方法。
研讀
研讀(study reading)就是仔細(xì)閱讀，對文章有透徹深刻的理解。根據(jù)考題，運用上下文、邏輯關(guān)系、背景知識進(jìn)行判斷和推論。對難句的理解和翻譯用得著這種方法。提高閱讀速度的一個重要內(nèi)容是擴大詞匯量。其必要性表現(xiàn)在以下幾個方面：
1. 詞匯量決定了你的閱讀理解能力，詞匯量越大，你閱讀得越廣，視野就越開闊，你閱讀理解的得分就越高。
2. 有限的詞匯量必然會影響你閱讀理解能力的提高。
生詞的含義只有在上下文中才能完全展現(xiàn)出來，并易于被識記、理解、掌握。換句話說，是上下文給某個詞以特定含義，而這個特定含義往往是字典無法提供的。有的人或許會說，我們從中學(xué)到大學(xué)英語詞匯都是通過背生詞表來記的。但是這樣說的讀者忽視了很重要的一點：所學(xué)課文后面的詞匯表都是為課文服務(wù)的，而且，教師上課時對某些詞或表達(dá)方式所舉的實例，實質(zhì)上是為它們設(shè)置上下文。不少教師鼓勵學(xué)生背句子、段落、或整篇文章，都是出于同一目的，即要學(xué)生在上下文中理解并掌握詞匯和短語。
3. 多讀是擴大詞匯量的最好的方法。不僅要讀不同體裁的書和文章，而且要多接觸不同題材，才能適應(yīng)考試的需要。
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