420 Chapter 21What types of NoNhumaN orgaNisms have
beeN bioeNgiNeereD?- Scientists have created transgenic bacteria, plants, and
numerous nonhuman animals. - Some of these genetic engineering efforts aim to develop
transgenic animals or animal cells capable of producing
medically useful substances. - Genetically engineered plants have a variety of traits, such
as resistance to disease and herbicides.
taKe-home messaGethe gene for human growth hormone into mice, the result
was the “super mouse” shown in Figure 21.22A. Recom-
binant DNA technology also has been used to transfer
human and cow growth hormones into pigs, which then
grow much faster. Transgenic goats (Figure 21.22B) produce
CFTR protein (used to treat cystic fibrosis), as well as drugs
that prevent dangerous blood clots. These and other medi-
cally useful engineered proteins show up in the goats’ milk.
People with hemophilia A now can obtain the needed
blood-clotting factor VIII from a drug that is produced by
hamster ovary cells in which genes for human factor VIII
have been inserted. Factor VIII produced in this way elimi-
nates the need to obtain it from human blood, and thus the
risk of transmitting blood-borne diseases.
Plants have been intriguing genetic engineers for a
long time. Researchers now routinely grow crop plants
and many other plant species from cells cultured in the
laboratory. They use a variety of methods to pinpoint genes
that confer useful traits, such as resistance to an herbicide.
Later, whole plants with the trait—such as the herbicide-
resistant cotton plants shown in Figure 21.22C—can be
grown from the cultured cells.engineering Bacteria, animals, and plants
n Any genetically engineered organism that carries one or
more foreign genes is transgenic.Bacteria were the first organisms to be bioengineered.
Plasmids in modified bacteria can carry a range of human
genes, which are expressed to produce large quantities of
useful human proteins. Many of these proteins, such as
human growth hormone, once were available only in tiny
amounts and were costly because they had to be chemically
extracted from endocrine tissues. Other human proteins
produced today by bacteria include insulin and interferons.
Many types of animal cells can be “micro-injected” with
foreign DNA. For instance, when researchers introduced21.11
Figure 21.22 Animated! These are just a few of the organisms
with new traits bestowed by genetic engineering. A Mouse
littermates. The larger mouse grew from a fertilized egg into which
the gene for human growth hormone had been inserted. B Myra,
a goat transgenic for human antithrombin III, an anticlotting factor.
C A bacterial gene conferred herbicide resistance to the green,
young cotton plants shown. The plants are surrounded by brown
dead ones that did not have a working version of the modified gene.
Farmers who grow this resistant cotton don’t need to apply as much
weed killer to their fields. D The chart lists a few genetically modified
crop plants approved by the USDA. (A: R. Brinster and R. E. Hammer, School of
Veterinary Medicine, University of Pennsylvania; B: Transgenic goat produced using nuclear
transfer at Biotherapeutics. Photo used with permission; C: Inga Spence/Science Source)
Tomato, potato, corn, rice, Resistance to weed-killing
sugar beet, canola bean, herbicides used in agriculture
cotton, flax croplands
Potato, squash, papaya More resistance to harmful
viruses, bacteria, and fungi
Tomato Delayed ripening; easier to
ship, with less bruising
Corn, chicory Plants cannot interbreed with
wild stocksUSDA-Approved Crop Plant Modified TraitDA BCCopyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).