The Major Types of Cloning Vectors

There are many types of cloning vectors, but the most commonly used ones are genetically engineered plasmids. Cloning is generally first performed using Escherichia coli, and cloning vectors in E. coli include plasmids, bacteriophages (such as phage λ), cosmids, and bacterial artificial chromosomes (BACs).

pBR322 is 4361 base pairs in length and has two antibiotic resistance genes – the gene bla encoding the ampicillin resistance (AmpR) protein, and the gene tetA encoding the tetracycline resistance (TetR) protein.

• Plasmid. Circular extrachromosomal DNA that autonomously replicates inside the bacterial cell.
• Phage. Linear DNA molecules derived from bacteriophage lambda.
• Cosmids.
• Bacterial Artificial Chromosomes.
• Yeast Artificial Chromosomes.
• Human Artificial Chromosome.

The P1-derived artificial chromosomes are DNA constructs derived from the DNA of P1 bacteriophage and BAC. They can carry large amounts (about 100–300 kb) of other sequences for a variety of bioengineering purposes. It is one type of vector used to clone DNA fragments (100- to 300-kb insert size; average, 150 kb) in E.

Vector size: The vector size range varies from 5 kb plasmid vectors to 6–10 megabases HAC high-capacity vectors….1.1 Introduction.

Yeast artificial chromosome (YAC): A vector (carrier) created and used in the laboratory to clone pieces of DNA. A YAC is constructed from the telomeric, centromeric, and replication origin sequences needed for replication in yeast cells.

Cloning sites-

• Cloning sites are the recognition sites of the restriction enzymes.
• The ligation of alien DNA is carried out at a restriction site present in one of the two antibiotic resistance genes.

Two types of vectors are most commonly used: E. coli plasmid vectors and bacteriophage λ vectors. Plasmid vectors replicate along with their host cells, while λ vectors replicate as lytic viruses, killing the host cell and packaging the DNA into virions (Chapter 6).

The pBR322 plasmid contains a gene that allow the bacteria to be resistant to the antibiotics tetracycline and amipicillin. To use pBR322 plasmid to clone a gene, a restriction endonuclease first cleaves the plasmid at a restriction site. Another plasmid used as a vector to clone DNA is called pUC18 plasmid.

The regula- tory DNA sequences involved are important to the plant but not to the bacterium. Consequently, the sequences are poten- tially of great use in cloning genes that can be expressed in plants. To induce tumours, Agrobacterium must contain a large, tumour-inducing plasmid, the Ti-plasmid.

order of synthesis

two selectable markers

4,361 base pairs

pBR322 has 20 known unique restriction sites (Only 5 shown in the diagram). 9 of these sites are within the tetracycline (Tcr) or ampicillin resistance (Apr) genes insertional inactivation….

Rop (also known as repressor of primer) is a small protein responsible for keeping the copy number of ColE1 and related bacterial plasmids low in E. coli.

pBR322 DNA is a commonly used plasmid cloning vector in E. coli (1). The molecule is a double-stranded circle 4,361* base pairs in length (2). pBR322 contains the genes for resistance to ampicillin and tetracycline, and can be amplified with chloramphenicol.

Plasmids

Plasmid

8. Which of the following is not a type of plasmid? Explanation: T4 is a bacteriophage, a virus which is also a desirable cloning vector just like a plasmid. T4 can be used in higher organisms and has a lysogenic life cycle and hence a vector of choice.

Solution : Plasmid is an extrachromosal genetic element of DNA that is capable of replicating independently of host chromosome. It forms the basis of many cloning vectors used in genetic engineering.

Plasmids are the most common vectors used in plant transformation. They are used to multiply the gene of interest and to transfer foreign genes into the recipient organism. Plasmids are small circular pieces of DNA found in almost all bacteria and in some fungi, protozoa, plants and animals.

Solution : In higher organism retroviruses vectors are used, while Baculovirus vectors are used for production of transgenic proteins in silkworm. …

The DNA of retrovirus is used as a vector as it has the ability to induce cancer. It is introduced to the host after the virus is disarmed and cannot cause cancer in the host cell. So, we deliver a piece of DNA into human lymphocytes with the help of retrovirus that acts as phage vectors.

There are many types of cloning vectors. Genetically engineered plasmids and bacteriophages (such as phage λ) are perhaps most commonly used for this purpose.

In general, cloning vectors are plasmids that are used primarily to propagate DNA. An expression vector is a specialized type of cloning vector. Expression vectors are designed to allow transcription of the cloned gene and translation into protein.