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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.
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发表于 2016-12-4 13:30:27