Vector (molecular biology)

Vector (molecular biology)

In molecular biology, a vector refers to a DNA molecule used as a vehicle to artificially carry foreign genetic material into another cell, where it can be replicated and/or expressed. A vector containing foreign DNA is termed recombinant DNA. The four major types of vectors are plasmids, viral vectors, cosmids, and artificial chromosomes. Each of these vectors has its own advantages and limitations in terms of capacity for genetic material, ease of manipulation, and efficiency of transformation. Vectors are chosen based on the specific needs of the molecular biology project.

Types of Vectors

Plasmids

Plasmids are small, circular, double-stranded DNA molecules that are distinct from the chromosomal DNA. They are most commonly found in bacteria but can also be found in archaea and eukaryotic organisms. Plasmids are capable of independent replication and are used extensively in the laboratory for the manipulation of genes. They are particularly useful for cloning small to medium-sized genes, gene expression studies, and generating transgenic organisms.

Viral Vectors

Viral vectors are tools commonly used by molecular biologists to deliver genetic material into cells. This process can be performed inside a living organism (in vivo) or in cell culture (in vitro). Viral vectors take advantage of the natural ability of a virus to inject its DNA or RNA into a host cell. By replacing the viral genome with the gene of interest, researchers can use the virus as a mechanism to get genetic material into the cells of the organism they are studying.

Cosmids

Cosmids are plasmid vectors that contain a small portion of bacteriophage λ DNA, which allows them to be packaged into λ phage particles for infection into E. coli. This method can increase the efficiency of DNA introduction. Cosmids can carry larger DNA fragments than plasmids, typically up to 45 kilobases, making them suitable for genomic library construction and physical mapping efforts.

Artificial Chromosomes

Artificial chromosomes, such as bacterial artificial chromosomes (BACs) and yeast artificial chromosomes (YACs), are vectors designed to carry large DNA fragments. BACs can carry DNA fragments of up to 300 kilobases, while YACs can carry up to 1 megabase of foreign DNA. These vectors are essential for mapping and sequencing large genomes, such as the human genome, and for the study of large gene clusters.

Applications

Vectors are used in a wide range of applications in molecular biology, including:

• Gene cloning
• Gene therapy
• Creation of transgenic organisms
• Functional analysis of genes
• Vaccine development

Choosing a Vector

The choice of vector for a particular project depends on several factors, including:

• The size of the DNA to be cloned
• The host organism to be transformed
• The need for expression of the cloned gene
• The requirement for stable or transient gene expression

Safety Considerations

The use of vectors, particularly viral vectors, in research and therapy is subject to strict safety and ethical considerations. The potential for insertional mutagenesis, immune response, and the possibility of generating replication-competent viruses are important factors that must be addressed.

See Also

• Recombinant DNA
• Gene therapy
• Transgenic organism
• Molecular cloning