If you had
a gene isolated that made an amazingly useful protein, wouldn't it
be great if you could somehow just make the stuff?
That was a question that arose as genes for important human proteins
were isolated and sequenced. Transcription and translation,
however, are not easily done in test tubes at a lab bench - living
cells would need to be used. It was already known that
bacteria can trade small gene packages, plasmids, that could
sometimes become integrated into the main chromosome, putting a new
gene into the genome. Procedures were developed to isolate
plasmids, clip out their genes, and insert the target genes.
Cultures would be exposed to the plasmids, but how to tell which
cells integrated the genes? Marker genes were added to
the plasmids. One common such gene produces a resistance
to a particular antibiotic. After plasmid exposure and culture
growth, the culture is dosed; cells that have not picked up
and used the plasmids have no resistance and die.
Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR
Cas-9, C-associated protein 9. For gene editing within an
existing genome, it is supposed to be cheaper, faster, more
reliable, and more efficient than other methods. The system was
adapted from a virus-defense system of bacteria – they clip out bits
of viral DNA to use as targets if the viruses invade again. RNA
binders are made with the viral DNA, and the Cas-9 comes in to
expedite cutting up the targeted section of virus DNA. In the lab
procedure, the RNA is from a targeted sequence in the target genome.
Cas-9 helps to cut the DNA at that spot, and enzymes from the normal
proofreading and repair systems can be used, clipping out pieces,
and new alleles can be spliced in where “bad” alleles have been.
Currently, the genes are in tissue cells, so the changes introduced
are not passable to offspring. The changes could be introduced into
embryos, though, and become part of a whole individual and
Information on bacterial transformation.
Using the technique to produce human insulin.
Introduction to CRISPR.
CRISPR patent issues.