Plasmid vector, artificial modification of plasmid vector

Plasmids are a type of covalent, closed, circular double stranded DNA molecules that naturally exist in bacterial and fungal cells and can replicate independently of chromosomal DNA, also known as ccDNA. Their size typically ranges from 1 to 600 kb.

Vector is a type of DNA molecule that can self replicate, in which a segment of DNA is removed without affecting its replication. It can be used to replace or insert exogenous (target) DNA and bring the target DNA into the host cell. Commonly used carriers include plasmids, bacteriophages, viruses, etc.

Plasmid vectors are artificially constructed plasmids based on natural plasmids to adapt to laboratory operations. Compared with natural plasmids, plasmid vectors typically carry one or more selective marker genes (such as antibiotic resistance genes) and an artificially synthesized polyclonal site sequence containing multiple restriction endonuclease recognition sites, while removing most non essential sequences to minimize molecular weight and facilitate genetic engineering operations.

Plasmid construction is a commonly used experimental technique in molecular biology research. The principle relies on the action of restriction endonucleases, DNA ligases, and other modifying enzymes. After appropriate cleavage and modification of the target gene and vector DNA, they are connected together and then introduced into the host cell to achieve correct expression of the target gene in the host cell.