Why are Plasmids and viruses used as vectors?

Answer 1

Transformation of bacteria plasmids are one of the easiest ways to demonstrate and test hypotheses about genetic transformations in laboratory conditions due to the ease of performing the procedure and relative quickness of obtaining results. DNA can be taken into the bacterium by subjecting the a competent cell to heat shock which makes the plasma membrane more fluid. (A bacterial cell may need to be treated with a chemical, ie) CaCl2 in E. coli, in order to become competent, or have enhanced ability for DNA uptake). The foreign DNA, or plasmid, will insert itself into the DNA of the bacterium. Bacterial cells have relatively few genes, compared to other organisms. Bacteria replicate frequently and will therefore express a phenotype in a reasonable amount of time. Only some competent cells will become transformed. This factor is expressed as transformation efficiency, which is defined by (# of transformants obtained)/(# of total cells).

Answer 2

Molecular biologists use bacterial plasmids as a "tool" to study DNA. Normal bacteria (like E. coli) will naturally replicate all the plasmids and nuclear DNA (genomic DNA) in the cell as they mature and prepare for cell division. We trick the E. coli host cells into replicating Recombinant (spelled correctly) DNA that we introduce by a process called transformation. For example: if we want to study a cancer gene, then we can splice it (called ligation) into an artificial plasmid DNA (called a vector) and introduce this into E. coli (called transformation). Then the E. coli will do us a huge favor by replicating our cancer gene of interest, so we can extract the cancer gene DNA and study it. It is a handy way to get enough DNA from a gene of interest to perform experiments on. These experiments might consist of sequencing the cancer gene DNA or re-introducing a large amount of the cancer gene DNA into a human cell line and then study different drugs that are also introduced to the human cell line.

Answer 3

They are already tailor-made to insert DNA into another organism. Scientists hijack their mechanism and replace the original DNA/RNA with their own.

Agrobacterium tumefaciens causes crown galls in some plants, by inserting its DNA into the plant's genome. To make a vector from this plasmid, researchers removed everything that was not essential for this "inserting of DNA" and replaced it with various other genes.

Answer 4

1) Plasmid is self replicating.

2) It contain various site for restriction endonucleases