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Genetic Technology
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Humans have been altering gene patterns since prehistoric times. This tinkering began with
farmers. They selectively bred their best plants and animals. This increased the frequency of
desirable traits. Today, scientists have taken this to another level. They can manipulate living
things on a gene-by-gene basis.
Genetic Analysis
A century ago, scientists glimpsed chromosomes through their microscopes. These cell structures
control heredity. First, geneticists learned what normal chromosomes look like. They then
studied abnormalities. An extra chromosome 21, for example, produces Down syndrome. This
disorder negatively affects learning and development. In 1966 doctors began offering prenatal
tests. These detected chromosome abnormalities.
Today, geneticists can read individual genes. Genes consist of DNA. This molecule consists of
nucleotides. In essence, nucleotides are genetic letters. They spell out the instructions for
building organisms.
DNA Sequencing
In the 1960s, geneticists discovered enzymes that cut DNA into pieces. By sorting these snippets,
geneticists worked out gene sequences.
DNA Fingerprinting
DNA fingerprinting is a kind of genetic analysis. It is famous for solving crimes. At a crime
scene, police collect genetic material. Often this is blood or other bodily fluids. In a laboratory,
the material is analyzed. Computers compare the DNA fingerprint against those of suspects. A
match leads to identification.
Genetic analysis can also reveal family relationships. Often, it is used to identify accident
victims. Similarly, biologists use it to compare species. It even helps in determining how certain
living things evolved.
The Miracle of PCR
In the 1980s, scientists developed ways to rapidly copy DNA fragments. This process is called
PCR. It stands for polymerase chain reaction. Scientists automated the process. They could then
copy DNA billions of times in a few hours. This sped up genetic research. It also reduced costs.
As a result, researchers could decode entire genomes. A genome is an organism’s complete set of
genes. By 2003 the human genome had been mapped.
Genetic Engineering
In the 1970s, researchers began using microbes to transfer genes between organisms. This
produces transgenic organisms. Transgenic bacteria were the first products of genetic
engineering. Some can produce human hormones. These hormones are then used to treat
diseases.
Next, genetic engineers developed transgenic plants and animals. These include crops that
produce their own pesticides. Some transgenic livestock produce drugs in their milk.
Gene Therapy
More than 4,000 diseases stem from genetic defects. Potentially, they can be cured by replacing
defective genes. During the 1990s the first experimental treatments were applied. But in 1999 a
patient died during an experiment. Investigators found other instances of dangerous reactions.
This threw the field into turmoil.
Since then, there have been successes. In 2000, French physicians used gene therapy to cure
infants with severe immunodeficiency disease. Still, gene therapy remains an inexact science.
Researchers continue to improve their techniques.
Cloning
Some organisms can reproduce by cloning. They generate exact copies of themselves without
sexual reproduction. Identical twins are also clones in that they develop from the same fertilized
egg.
Today, scientists can produce clones from ordinary cells taken from parent organisms. They do
so by tricking the mature cell into reverting to an earlier stage of development. In essence, the
cell activates the genes responsible for creating a new organism. Normally, such genes turn off
after embryonic development.
In 1996, Dolly became the first cloned mammal. She was cloned from the cell of an adult sheep.
Scientists have since cloned dogs, cats, deer, horses, pigs, bulls, and goats. Biotechnology
companies have also used cloning to reproduce transgenic livestock.
Ethical Concerns
Genetic technology raises many ethical issues. Chief among these is interest in cloning humans.
This may be of special interest to infertile couples. At present, many people consider human
cloning unethical.
Others worry that our ability to tinker with human genes could go too far. Few would argue
against banishing genetic diseases. But what other traits might be judged undesirable? Should we
even be making such judgments?
Meanwhile, ethicists warn against allowing employers or insurers to use genetic tests. This might
allow them to discriminate against those with markers associated with certain diseases.
Yet another debate rages about the use of human embryonic stem cells. These cells may enable
researchers to generate replacement organs and cure disease. But their use involves the
destruction of embryos. Embryos consist of small cell clusters that grow from fertilized eggs.
Some people believe that destroying them is liking killing a person.
Still others worry about the problems that might result when transgenic crops spread their genes
to other plants. Clearly, genetic technology holds great promise—but also many questions—for
future generations.
How to cite this article:
MLA (Modern Language Association) style:
"Genetic Technology." The New Book of Knowledge. Grolier Online, 2013. Web. 16 Jan. 2013.
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