Given the large number of tree genes and the little that is known about them, tree engineersare starting with a search for genetic "markers". The first step is to isolate DNA from treeswith desirable propertiessuch as insect resistance. The next step is to find stretches of DNAthat show the presence of a particular gene. Then, when you mate two trees with differentdesirable properties, it is simple to check which offspring contain them all by looking for thegenetic markers. Henry Amerson, at North Carolina State University, is using genetic markersto breed fungal resistance into southern pines. Billions of these are grown across America forpulp and paper, and outbreaks of disease are expensive. But not all individual trees aresusceptible. Dr. Amerson’s group has found markers that distinguish fungus-resistantstock from disease-prone trees.Using traditional breeding techniques, they are introducingthe resistance genes into pines on test sites in America.

　　Using generic markers speeds up old-fashioned breeding methods becauseyou no longer haveto wait for the tree to grow up to see if it has the desiredtraits. But it is more a sophisticatedform of selective breeding. Now. however.interest in genetic tinkering (基因修補) is also gainingground. To this end, Dr.Amerson and his colleagues are taking part in the Pine Gene DiscoveryProject. an initiative to identify and sequence the 50,000-odd genes in the pine tree'sgenome. Knowing which gene does what should make it easier to know what to alter.

　　如果你今天走到森林里去，可能會看到高科技的樹木——這些樹通過基因改良促進了生長的速度或提高了木材的質量。基因改造的糧食作物在過去十年里雖然備受爭議，卻已經越來越普遍，[1]而樹木的基因改造工程相對來說還是比較滯后。

　　這其中一個原因是技術問題。了解并改變一棵大松樹的基因比制造品質優良的馬鈴薯復雜多了。馬鈴薯可在實驗室里迅速發芽生長，[2]但要在試管里把經過基因改造的細胞培育成一棵大樹卻不是幾個月就能完成的，要花上好幾年的時間呢。而且，對于樹木的基因，我們知之甚少。有些樹，比如松樹，帶有大概相當于人類10倍那么歲的DNA。[3]人類染色體工程中分離和排列人類細胞里大概10萬個基因的工作已經進展到一半了，而用同樣的方法分析樹種基因還只是處在萌芽階段。

　　雖然樹木的基因數量巨大，而我們也知之甚少，但是樹木基因工程的研究人員正開始尋找基因“標記”。第一步，先把具有優良特性(如具有害蟲抵抗性)樹種的基因分離出來：下一步，找出帶有這個優良基因的DNA片段;接著，讓兩棵具有不同優良特性的樹種雜交，之后通過尋找當中的基因標記就能輕易確定哪棵雜交樹苗具有所有特性。北卡羅來納州立是學的Henry Amerson正運用基因標記技術培育能抵抗真菌的南方松樹。這個樹種的生長遍布美國，用于制造紙漿和造紙，所以一旦染病，代價昂貴。[4]但是，這種樹卻不是每一棵都容量染病。Amerson博士的研究小組已經找到區別抗真菌和易染病的樹種的基因標記。他們正利用傳統的繁殖技術，把這種抗病基因推廣到美國的松樹試驗場。

　　使用基因標記技術，可以加快舊式繁殖的速度，因為你不用等待樹苗長大才能看到它是否帶有那些你想要的特性。但事實上，這是一種更為復雜的選擇性繁殖的技術。不過現在對于基因修補技術的研究也正在升溫。[5] 為實現這一目標，Amerson博士和他的同事們正參與一個名為“發現松樹基因”的研究工程，其宗旨是為了辨別和排列松樹染色體組中的5萬余個基因。如果能知道每個基因的功能，就能更容易地知道應該改變哪個基因了。

　　1. Compared with genetic engineering of foodcrops, genetic engineering oftrees____________________.

　　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.