A plasmid is a ring-shaped piece of DNA found in bacteria, fungi, and even some plants. Plasmids float freely in the cell and are independent from the chromosomal DNA.
A plasmid does not contain genetic information that is essential for the organism’s survival. Genes in a plasmid are split up into two categories- 1. Backbone Genes – contain info for transfer and upkeep of the plasmid 2. Accessory Genes – contain info for beneficial effects such as antibiotic resistance; even though these genes are not necessary, they may be advantageous in the fight for food and space
Plasmids can be transferred from cell to cell. This ability is what lets bacteria adapt to new environments extremely quickly. The process by which a plasmid is shared is called conjugation. The DNA is split into two strands, one stays in the donor cell and the other is given to a recipient cell through what is called the mating bridge, or pilus, connecting the two cells. The strands are then used as a template to copy the DNA and form two strands once again. Conjugation In-Depth Animation
In 1959, Japanese scientists were confused as to why the antibiotic used against dysentery was not working on select patients. After some testing, they found that the strain of the bacteria infecting their patients had a gene for resistance on the plasmid against the antibiotic used. This helped form the conclusion that genes of resistance are always found on the plasmid.
Although plasmids can carry genes that make antibiotics ineffective, we can use them for research in a positive way. This is when we use what is called recombinant DNA.
Recombinant DNA is a plasmid that has had foreign genes added to it. Recombinant DNA can be used to create massive amounts of proteins for research, and has also been used to add genes to organisms or cells.
To create recombinant DNA you must use restriction enzymes to cut the plasmid and the DNA containing the desired gene. “Sticky Ends” form where the plasmid was cut with the restriction enzymes which allow you to splice in the desired gene. Then you can insert the plasmid into a cell to take effect. bio.miami.edu
Proteins are often being studied by researchers. However, before genetic engineering, they were produced in insufficient quantities and researchers had to dig through tons of biomass to get a usable quantity. Even with proteins in such small amounts, the purity of the proteins was still very poor.
To get mass quantities of a protein, a scientist can do the following- 1. Get the gene for a protein from an animal that produces it naturally. 2. Use restriction enzymes to cut the plasmid and splice the gene into place. 3. Insert the plasmid into an E. Coli bacteria and let it multiply.
Cardiomyocytes – heart muscle cells that allow your heart to beat. Researchers at Johns Hopkins Medical Institutions have created these cells with plasmids. Cardiomyocytes can be used in transplants and for testing heart drugs, which is much needed in today’s popsci.com world.
The Researchers from Johns Hopkins took blood, stem cells, and plasmids. Then, seven genes were added to the plasmids. The plasmids were placed into the stem and blood cells, which were allowed to grow and multiply in a broth to simulate embryonic conditions.
Boyle, Rebecca. "Popular Science | New Technology, Science News, The Future Now." Popular Science | New Technology, Science News, The Future Now. Popular Science, 8 Apr. 2011. Web. 10 May 2012. <http://www.popsci.com/technology/article/2011-04/new- cell-building-method-turns-blood-cells-directly-beating-heart- cells-using-rings-dna>. "Genetic Engineering." Science Clarified. Advameg, 2012. Web. 22 May 2012. <http://www.scienceclarified.com/scitech/Genetics/Genetic- Engineering.html>. "Plasmid." BookRags. BookRags, 2012. Web. 9 May 2012. <http://www.bookrags.com/research/plasmid-gen-03/>. "Plasmids - The Virtual Genome Project." Plasmids -The Virtual Genome Project. University of Idaho. Web. 23 May 2012. <http://people.ibest.uidaho.edu/~etop/vgp/plasmids.html>.