Cloning Vectors – CBSE Notes Class 12

Cloning vectors are small piece of DNA molecule which is used to carry foreign DNA into the host cell which consists of a capability of self-replication and integration into the host cell. These vectors are used in the analysis of the molecular structure of DNA. The target DNA in the vector is integrated into the specific sites of this vector and ligated by DNA ligase. Phages and Plasmids are examples of cloning vectors.

What is Cloning Vectors?

A Cloning vector is a DNA molecule that is used to carry foreign DNA into the host cell. They are mainly small pieces of DNA molecules that have the ability to self-replicate and integrate into the host cell. Vectors can be plasmid from the bacterium which is a cell from higher organisms. The target DNA in the vector is inserted into the specific sites of this vector and ligated by DNA ligase. After that for replacement vector is changed into the host cell.

Features of Cloning Vectors

The process of cloning is performed by using E. coli. Cloning of vectors consists of a system that permits function and maintenance in E.coli. Some of the other features are mentioned below:

• Vectors should be small in size so that they can easily integrate into the host cell.
• They should consists of a multiple sites for cloning and also consists of a restriction site for the insertion of target DNA.
• Integration of Donor DNA should not interfere in the replication procedure of cloning in vector.
• Cloning DNA consists of origin of replication so that they can self replicate inside the host cell.
• They should consists of selectable marker with antibiotic resistance gene which facilitates screening of recombinant organisms.

Types of Cloning Vectors

There are different types of cloning vectors which are mentioned below:

Plasmid

Plasmids are the first vectors which are used in gene cloning which are found in the bacteria, eukaryotes and archaea. These are consist of antibiotic resistant genes. They are self replicating DNA molecules which are also extrachromosomal. Some examples of plasmids are- pBR322, pUC18 and F-plasmid.

Bacteriophage

Bacteriophage are better in efficiency when compared to the plasmids for cloning large DNA inserts. DNA of 53kb can be packed in bacteriophage. Screening of phage plaques are easier than the screening of recombinant bacterial colonies. M13 phage is an example of bacteriophage.

Phagemids

Phagemids are known as artificial vectors which are used in the combination of M13 phage. They consists of multiple cloning sites .They are identified by the blue white screening.

Bacterial Artificial Chromosomes

Bacterial Artificial chromosomes (BAC) are generally obtained from F’ plasmid which is a DNA molecule that has been produced and used to clone DNA sequences in bacterial cells. They are used to study about genetic disorders and also they are similar to E.coli plasmid vectors.

Yeast Artificial Chromosomes

These are the molecules used in mapping and sequences of genomes. They are designed by human being and they are used for cloning of DNA sequences in yeast cells.

Cosmid

Cosmid consists of similar features of both plasmid and phase and they have a cloning limit of 30 kb to 50 kb.

Human Artificial Chromosome

Human Artificial Chromosome are used to transfer human genes as they carry large portion of DNA hence they are not restricted to cloning.

FAQs on Cloning Vectors

1. What do you mean by Cloning vectors ?

Answer:

Cloning vectors is defined as a small piece of DNA molecule which is used to carry a foreign DNA into the host cell which consists of a capability of self replication and integration into the host cell. They can be plasmid from the bacterium which is a cell from higher organisms.

2. Name the types of Cloning vectors ?

Answer:

There are different types of cloning vectors are which are as follows – Plasmid, Bacteriophage, Bacterial Artificial chromosomes, Yeast Artificial Chromosomes, Phagemids, Cosmids, Human Artificial Chromosome and Retroviral vectors.

3. Write two characteristics of cloning vectors ?

Answer:

The two characteristics of cloning vector are as follows:

• The Vectors should be small in size so that they can easily integrate into the host cell.
• They should consists of a multiple sites for cloning. Cloning DNA consists of origin of replication so that they can self replicate inside the host cell.

4. What is the importance of Bacteriophage in cloning vectors ?

Answer:

Bacteriophage are better in efficiency when compared to the plasmids for cloning large DNA inserts. DNA of 53kb can be packed in bacteriophage. Screening of phage plaques are easier than the screening of recombinant bacterial colonies. M13 phage is an example of bacteriophage.

5. Which is the first used cloning vector ?

Answer:

The first artificial used cloning vector is pBR322. It is a common plasmid which is used in E.coli. It has many application in cloning vectors due to their manageable size. It was created in 1977 by Herbert Boyer. It has high copy number which is useful in genetic engineering.

6. Write the features of plasmid which are used as cloning vector ?

Answer:

The features of plasmid used as cloning vector are:

• They should consists of an origin of replication.
• They should consists of restriction sites.