Biotechnology Products

Bacteria, plants and animals are genetically engineered to produce biotechnology products. Free-living organisms in the environment that have had a foreign gene inserted into them are called transgenic organisms.

Transgenic Bacteria

Recombinant DNA technology is used to produce bacteria that produce in large vats called bioreactors. If the foreign genes is replicated and actively expressed, a large amount of protein products can be obtained. The biotechnology products now available include hormones and similar types of proteins and vaccines.

Protection and Enhancement of Plants

Genetically engineered bacteria can be used to promote the health of plants. For example, bacteria that normally live on plants and encourage the formation of ice crystals have been changed from frost-plus to frost-minus bacteria. Field tests showed that these genetically engineered bacteria protect the vegetative parts of plants from frost damage. Also, a bacterium that normally colonizes the roots of corn plants has now been endowed with genes (from another bacterium) that code for an insect toxin. The toxin is expected to protect the roots from insects.

Bioremediation

Bacteria can be selected for their ability to degrade a particular substance, and then this ability can be enhanced by genetic engineering. For instance, naturally occurring bacteria that eat oil can be genetically engineered to do an even better job of cleaning up beaches after oil spills. Industry has found that bacteria can be used as biofilters to prevent air borne chemical pollutants from being vented into the air. They can also remove sulfur from coal before it is burned and help to clean up toxic waste dumps. One such strain was given genes that allowed it to clean up levels of toxins that would have killed other strains. Further, these bacteria were given “suicide” genes that caused them to self-destruct when the job had been accomplished.

Chemical Production

Organic chemicals are often synthesized by having catalysts act on precursor molecules or by using bacteria to carry out the synthesis. Today, it is possible to go one step further and to manipulate the genes that code for these enzymes. For instance, biochemists discovered a strain of bacteria that is especially good at producing phenylalanine, an amino acid needed to make aspartame, the dipeptide sweetener better known as NutraSweet. They are isolated, altered, and formed a vector for the appropriate genes so that various bacteria could be genetically engineered to produce phenylalanine.

Mineral Processing

Many major mining companies already use bacteria to obtain various metals. Genetic engineering may enhance the ability of bacteria to extract copper, uranium, and gold from low-grade sources. Testing of genetically engineered organisms having improved bleaching capabilities is in progress.

Transgenic Plants

Protoplasts: The only possible plasmid for genetically engineering plant cells belongs to the bacterium Agrobacterium, which will infect many but not all plants. Therefore, other techniques have been developed to introduce foreign DNA into plant cells that have had the cell wall removed and are called protoplasts. It is possible to treat protoplasts with an electric current while they are suspended in a liquid containing foreign DNA. The electric current makes tiny, self-sealing holes in the plasma membrane through which genetic material can enter. Then a protoplast will develop into a complete plant.

Presently, about 50 types of genetically engineered plants that resist insects, viruses, or herbicides have entered small-scale field trials. The major crops that have been improved in this way are soybean, cotton, alfalfa, rice, potato; and corn. Plants have been engineered to produce human proteins, such as hormones, in their seeds. A weed called mouse-ear cress has been engineered to produce a biodegradable plastic (polyhydroxybutyrate, or PHB) in cell granules.

One type of antibody made by corn can deliver radio isotopes to tumor cells, and another made by soybean can be used as treatment for genital herpes (caused by herpes simplex type 2 virus tiny, painful blisters appear on genitals.). Plant made antibodies are inexpensive and there is little chance that contamination with pathogens infect people.

Transgenic Animals

Genetically Engineered Goats

Animals, too, are being genetically engineered. Because animal cells will not take up bacterial plasmids, the method used to insert genes into their eggs is vortex (a whirling motion of a liquid) mixing. The eggs are placed in an agitator with DNA and silicon-carbide needles, and the needles make tiny holes through which the DNA can enter. Using this technique, many types of animal eggs have taken up bovine (cattle) growth hormone (rbGH). The procedure has been used to produce large fishes, cows, pigs, rabbits, and sheep. Genetically engineered fishes are now being kept in ponds that offer no escape to the wild because there is much concern that they will upset or destroy natural ecosystems.

Gene Pharming

The use of transgenic farm animals to produce pharmaceuticals, is being pursued by a number of firms. It is advantageous to use animals because the product is obtainable from the milk of females. Genes that code for therapeutic and diagnostic proteins are incorporated into the animal's DNA, and the proteins appear in the animal's milk. In one instance a bull was genetically engineered to carry a gene for human lactoferrin, a drug for gastrointestinal tract infections, and he passed the gene to many offspring, among them were several females.

Procedure of Producing Transgenic Mammals

DNA containing the gene of interest is injected into donor eggs. The fertilization takes place in vitro. The zygotes are placed in the uterus of the host female where they develop. On maturation of the female offspring the product is secreted in the milk. Scientists have been able to genetically engineer mice to produce human growth hormone in their urine instead of milk, as urine is produced in large quantities by all the individuals and it is easier to extract.

Cloning of Transgenic Animals

Cloning means ‘making identical copies’. When an embryo first grows from a fertilized egg, all of its cells have the same DNA and are much alike. Then different embryonic cells start using different parts of their DNA. Their unique selections commit them to become liver cells, heart cell, brain cell etc.

In 1997 in Scotland, a research group led by Wilmut at the Roslin institute in Scotland cloned a sheep. The scientists first removed the haploid nucleus from an unfertilized sheep egg. They then inserted into the egg another nucleus taken from an udder (the organ containing the mammary glands of sheep, cow, mare etc., having more than one teat) cell. The egg become diploid, having a diploid nucleus containing two copies of every chromosomes, just as a fertilized egg would. The egg was then implanted into another female sheep. The lamb was named Dolly, which developed into a healthy adult and gave birth to a lamb of her own.

In 1998 Ryuzo Yanagimachi and his co-workers at the University of Hawaii cloned three generations of mice. They quickly transferred nuclei from mature cumulus cells from an ovary into unfertilized, enucleated egg. (Cumulus cell provide nutritional support to neighboring egg). Shortly afterward, they chemically activated the eggs, which developed into fully formed mice. Scientists in japan slipped nuclei from a cow's cumulus cells and oviduct cells into enucleated eggs. These were transferred to surrogate (a female who bears a baby after implantation embryo from another female) cow mother. Four cloned calves have survived. Cloning of human is banned.