(i) Should have ori / origin of replication, - Has selectable marker, genes encoding for an antibiotic resistance / genes encoding for α- galactosidase, -Has cloning site/recognition site, for the restriction enzyme to recognise.
(ii) DNA is a hydrophilic molecule
Bacterial cell is made competent by treating with specific concentration of Ca++ ion/divalent ions, incubating them on ice, heat shock for a short period and placing it back once again.
Detailed Answer:
The following are the features that are required to facilitate cloning into a vector :
(a) Origin of replication (ori) : This is a sequence from where replication starts and any piece of DNA when linked to this sequence can be made to replicate within the host cells. This sequence is also reiponsible for controlling the copy nurnber of the linked DNA.
(b) Selectable marker : The vector requires a selectable marker, which helps in identifying and eliminating non transformants and selectively permitting the growth of the transformants. Transformation is a procedure through which a piece of DNA is introduced in a host bacterium. Normally, the genes encoding resistance to antibiotics such as ampicillin, chloramphenicol, tetracycline or kanamycin, etc', are considered useful selectable markers for E, coli.
(c) Cloning sites : In order to link the alien DNA, the vector needs to have very few recognition sites for the commonly used restriction enzymes. Presence of more than one recognition sites within the vector will generate several fragments, which will complicate the gene cloning.
