Earth Science: Human – Gene Technology
With modern gene technology it is now possible to selectively intervene in an organism’s hereditary information or its biochemical control mechanisms.
Genes and their regulators can be isolated and altered to produce particular genetic products, such as antibiotics, human insulin, or monoclonal antibodies in large quantities.
Earth Science: Biology – Genetics and Heredity – Cloning
The age of modern gene technology began in the 1960s, with the discovery of the restriction enzyme, which enabled the selective production of DNA fragments. A number of other advances have furthered genetic technicians.
The cloning of genes-the integration of a particular DNA fragment in a transport medium (vector) for DNA and a subsequent transfer of the constructed fragment into a receiver cell-became possible when the first restriction enzyme (restriction endonuclease) was identified and described.
These cut nucleic acids at very specific locations, so that afterward precisely defined partial fragments are available. If restriction endonucleases cut both strands of a DNA double-strand with their bases offset, so-called sticky ends are formed (with a single strand overhanging the end sections). In the event of a straight cut, one talks about blunt ends.
Subsequently, certain enzymes called ligases can rejoin the ends again. Restriction enzymes occur naturally in bacteria. Other important tools for geneticists are vectors (bacteriophages and plasmids), which are transport systems that can be used to funnel DNA fragments into a cell.
Once these have been placed into a cell, the geneticist must ensure that it reproduces extrachromosomally, or that it becomes built into the genome.
Polymerase chain reaction
Another method commonly used is polymerase chain reaction (PCR) for the multiplication of specific DNA fragments, in which the target sequence is always doubled in successive cycles.
A very small amount of DNA produces so much material within a short time that evidence of a particular DNA segment can be identified, for instance, by means of staining or agarose gel electrophoresis. In order to duplicate DNA, one utilizes primers (oligonu-cleotides), which attach themselves specifically to complementary sequences from the entire DNA in the sample.
The primers are then lengthened by a DNA-dependent DNA-polymerase so that a copy is made. Subsequently, both strands are separated again by heat, so that a new cycle can take place.
BASICS
INSULIN SOURCES While insulin tor diabetic patients was formerly obtained from the pancreas of slaughtered animals, human insulin is now available for treatment, made from bacteria using new genetic-engineering methods.