Test: Tools of Recombinant DNA Technology: Cloning Vectors - Grade 12 MCQ

Plasmids and bacteriophages can replicate within bacterial cells without the help of chromosomal DNA. Thus they are self-replicating and autonomous in nature. They have their own replication machinery.

The sequence of DNA from where the replication starts is called the origin of replication. It is also written as ‘ori’. It is also responsible for controlling the copy number of target DNA. Bacteria usually have only one origin of replication.

A selectable marker is a gene that helps in identifying successful transformants. They eliminate the growth of non-transformants and favor the growth of the desired organism. It is one of the features which facilitate cloning in a vector.

Genes coding for resistance to antibiotics are usually used as selectable markers. They are introduced in an organism especially bacteria along with plasmid. They help in the identification of transformants.

Transformation is a process in which a foreign DNA is directly picked up by the bacteria from the surrounding environment. It leads to a change in the characteristics of bacteria. It was first observed by Griffith in 1928.

Recognition site is the sequence of DNA where the DNA is cleaved. The presence of more than one recognition site will lead to several cuts within DNA leading to fragmentation of DNA. This will complicate the process of gene cloning.

The Ti plasmid in Agrobacterium tumifaciens leads to tumor formation in dicots. ‘Ti’ stands for tumor-inducing. It may contain more than one T-DNA region. This plasmid is modified and used as a cloning vector.