Question

Which vector is best insertional or replacement vector?

Answer 1

Answer:

Explanation:

In λ Insertion vectors,no phage DNA is removed and foreign DNA fragments are inserted. They have a single recognition site for one or more restriction enzymes that cuts it only once. The foreign DNA fragments are inserted into this site in theλgenome. Since phage DNA is not removed there is a limit on the size of insert that can be cloned in this vector. They are generally utilized for construction of cDNA libraries from eukaryotic mRNA sequences.Example-λt10 and Charon16A.

Whereas λ Replacement or Substitution vectors were developed in which a middle dispensable ‘filler’ fragmentis is discarded and replaced with the insert DNA.These vectors contain restriction sites flanking the non-essential region of phage. They can accommodate larger inserts than insertion vectors. The middle region which is replaced by foreign DNA usually contains a gene that makes the phage non-viable in an appropriate bacterial host. Therefore vector molecules which do not contain foreign DNA can be selected against vector molecules containing foreign DNA, which will be viable.They are generally utilized for construction of genomic libraries. Examples-EMBL4 and Charon40.