Give a brief account of the tools of recombinant DNA technology.

Tools of recombinant DNA technology are :
i) Restriction enzymes
ii) Polymerase enzymes
iii) Ligases
iv) Vectors
v) The host organism.

i) Restriction enzymes 
Restriction endonucleases also called as restriction enzymes. These enzymes cut the long, linear DNA molecule into fragments. These enzymes can recognizes a specific nucleotide sequence called palindrome sequence. 
Example: EcoRI. 

ii) A polymerase is an enzyme that synthesizes long chains of polymers or nucleic acids. 

iii) Ligases are enzymes that are capable of catalyzing the reaction of joining two large molecules by establishing a new chemical bond

iv) Cloning Vectors
The DNA used as a carrier for transferring a fragment of foreign DNA into a suitable host is called vector.
Vector used for multiplying the foreign DNA sequences are called cloning vectors.
Example: plasmids, bacteriophages, cosmids and artificial chromosomes etc.
Characteristic features of vector :
* Should have low molecular weight.
* Should contains one (or) two selectable markers (genes encoding antibiotic resistance).
* Should contains origin of replication (ORI).
* Should contains restriction sites for endonucleases for incorporation of desired genes.
* Should be easy to isolate and purify.
* Ti plasmid of Agrobacterium tumifaciens is used  to deliver desired gene into plants and disarmed retrovirus are now used to deliver desired genes into animal cells.

v) Competent Host 
* To introduce the recombinant DNA into the bacterial cells, they should be made competent to take up DNA.
* This is done by treating them with a specific concentration of calcium ions which increases the efficiency of uptake of DNA by bacteria through pores of its cell wall.