Visualizing Environmental Science

PROCESS DIAGRAM

Genetic engineering differs from traditional breeding

methods in that desirable genes from any organism can be

used, not just those from the species of the plant or animal

being improved. If a gene for disease resistance found in

soybeans would be beneficial to tomatoes, a genetic engi-

neer can splice the soybean gene into the tomato plant’s

DNA (Figure 14.12). Traditional breeding methods

could not do this because soybeans and tomatoes belong

to separate groups of plants and do not interbreed.

Genetic engineering has the potential to produce

more nutritious food plants that contain all the essential

amino acids (which no single food crop currently does)

or that would be rich in necessary vitamins. Crop plants

resistant to viral diseases, drought, heat, cold, herbi-

cides, salty or acidic soils, and insect pests are also being

developed.

Genetic Engineering: A Solution

or a Problem?

Genetic engineering is a controversial technology that

has begun to revolutionize medicine and agriculture. The

agricultural goals of genetic engi-

neering are not new. Using tradi-

tional breeding methods, farmers

and scientists have developed

desirable characteristics in crop

plants and agricultural animals

for centuries. It takes time—15

years or more—to develop such

genetically improved organisms

using traditional breeding meth-

ods. Genetic engineering has the potential to accomplish

the same goal in a fraction of that time.

genetic

engineering The

manipulation of

genes (for example,

taking a specific gene

from one species

and placing it into an

unrelated species) to

produce a particular

trait.

362 CHAPTER 14 Agriculture and Food Resources

This example of genetic engineering uses a plasmid, a small circular molecule of DNA (genetic

material) found in many bacteria. The plasmid of the bacterium Agrobacterium introduces into a

plant desirable genes from another organism.

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✓✓THE PLANNER

Plant cells divide in tissue culture;

each cell contains the foreign gene.

Using tissue culture techniques,

cells are regenerated into plants.

Genetically modified plants are then

produced from the cultured plant cells.

Plasmid is inserted

into Agrobacterium.

Agrobacterium transfers

plasmid to plant cell.

Foreign gene is inserted

into the plant’s chromosome.

Plasmid

Agrobacterium

chromosome

Plasmid

Foreign gene

from soybean

codes for

desirable trait

Nucleus

Plant cell

Recombinant

plasmid

Chromosome

The foreign DNA is

spliced into a plasmid.

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567

How does the bacterium Agrobacterium

help scientists produce genetically modified plants?

Think Critically