Cloning Vectors.
1. Plasmids and bacteriophages are the commonly used vectors
2. Presently genetically engineered/synthetic vectors are also used for easily linking the foreign DNA and selection of recombinants from non-recombinants.
3. The following features are required to facilitate cloning in a vector:
(i) Origin of replication (Ori)
(ii) Selectable marker
(iii) Cloning (Recognition) site
(iv) Small size of vector.

All vectors that are used for propagation of DNA inserts in a suitable host are called cloning vectors. When a vector is designed for the expression of, i.e., production of the protein specified by, the DNA insert, it is termed as expression vector.

Agrobacterium tumefaciens is a plant pathogenic bacterium which can transfer part of its plasmid DNA because it infect host plants. Agrobacterium produce crown gall in most of the dicotyledonous plants. These bacteria contain large tumours inducing plasmid (Ti-plasmids) which pass on their tumour causing gene into genomeofhost plant. Thus gene transfer is happening in nature without human involvement hence Agrobacterium mediated genetic transformation is described as natural genetic engineering plants.

(i) Microinjection
(ii) Biolistics/ gene gun
(iii) Heat-Shock method
(iv) Using  disarmed pathogen vectors.

(a) (i) Denaturation
(ii) Annealing
(iii) Extension.
(b) Thermus aquaticus, it remains active during the high temperature, (induced to denature double stranded DNA) and catalyses polymerisation of DNA.

The first letter of the name comes from the genus of the bacterium.
The second and third letters come from the name of the species of the prokaryote cell from where it is isolated.
The next letter comes from the strain of the prokaryote.
The Roman Numbers following these four letters indicate the order in which the enzymes were isolated from that strain of the bacterium, e.g. EcoRI is isolated from E. coli, R Y 13.

The processes included under biotechnology are:
(i) Recombinant DNA (rDNA) vaccines.
(ii) Synthesis of a gene and introduction of it into a target cell.
(iii) Gene therapy.
(iv) In vitro fertilisation for production of test-tube babies.
(v) Production of many other biological compounds like hormones, insulin, growth hormone, etc.

Polymerase Chain Reaction:
Multiple copies of the desired gene or segment of DNA, can be synthesised in vitro using two sets of primers, the oligonucleotides that are complementary to the regions of DNA of the two strands and the enzyme DNA polymerase.
This enzyme extends the primers using the nucleotides provided in the reaction and the genomic DNA as the template.
For repeated amplification to be achieved, a thermostable DNA polymerase (Taq polymerase), extracted from the bacterium, Thermus aquaticus is employed; it remains active during the high temperature treatment used for denaturation and separation of the two strands.

Polymerase Chain Reaction:
Multiple copies of the desired gene or segment of DNA, can be synthesised in vitro using two sets of primers, the oligonucleotides that are complementary to the regions of DNA of the two strands and the enzyme DNA polymerase.
This enzyme extends the primers using the nucleotides provided in the reaction and the genomic DNA as the template.
For repeated amplification to be achieved, a thermostable DNA polymerase (Taq polymerase), extracted from the bacterium, Thermus aquaticus is employed; it remains active during the high temperature treatment used for denaturation and separation of the two strands.

Small volume cultures cannot yield appreciable quantities of products. To produce these products in large quantities the development of 'bioreactors' was required where large volumes (100-1000 litres) of culture can be processed. Thus bioreactors can be thought of as vessels in which raw materials are biologically converted into specific products, using microbial, plant, animal or human cells or individual enzymes.
Role. A bioreactor provides the optimal conditions for achieving the desired product by providing optimum growth conditions (temperature, pH, substrate, salts, vitamins, oxygen). One of the most commonly used bioreactor is of stirring type. A stirred tank reactor is usually cylindrical or with a curved base to facilitate the mixing of the reactor contents. The stirrer facilitates even mixing and oxygen availability throughout the bioreactor. Alternatively air can be bubbled 1lhroughthe reactor. If you look at the figure closely you will see that the bioreactor has an agitator system; an oxygen delivery system, a foam control system, a temperature control system, pH control system, sampling ports so that small volumes of the culture can be withdrawn periodically.

Small volume cultures cannot yield appreciable quantities of products. To produce these products in large quantities the development of 'bioreactors' was required where large volumes (100-1000 litres) of culture can be processed. Thus bioreactors can be thought of as vessels in which raw materials are biologically converted into specific products, using microbial, plant, animal or human cells or individual enzymes.
Role. A bioreactor provides the optimal conditions for achieving the desired product by providing optimum growth conditions (temperature, pH, substrate, salts, vitamins, oxygen). One of the most commonly used bioreactor is of stirring type. A stirred tank reactor is usually cylindrical or with a curved base to facilitate the mixing of the reactor contents. The stirrer facilitates even mixing and oxygen availability throughout the bioreactor. Alternatively air can be bubbled 1lhroughthe reactor. If you look at the figure closely you will see that the bioreactor has an agitator system; an oxygen delivery system, a foam control system, a temperature control system, pH control system, sampling ports so that small volumes of the culture can be withdrawn periodically.

(a) Engineered vectors are preferred because they help easy linking of foreign DNA and selection of recombinants from non-recombinants.
(b) Ori
It is a sequence of bases on DNA from where replication starts; any piece of DNA when linked to this sequence can be made to replicate within the host cells. This sequence also controls the copy number of linked DNA. 
Selectable marker 
The selectable marker helps in identifying and eliminating non-transformants or non-recombinants and permits selectively the growth of only recombinants.
Cloning sites
Cloning sites are necessary to link the alien DNA. Single recognition sites are commonly preferred.
When an alien DNA is introduced into the coding sequence of an enzyme or an antibiotic resistance, there is insertional inactivation; the enzyme is inactivated or the antibiotic resistance is lost and hence, recombinants can be selected from the non-recombinants.

1. Bioreactors can be considered as vessels in which raw materials are biologically converted into specific products using microbial, plant or human cells.
2. A bioreactor provides optimal conditions for achieving the desired product by I providing optimum growth conditions, pH, substrate salts, vitamins, oxygen, etc.
3. The commonly used bioreactors are of stirring type. A stirred-tank reactor is usually cylindrical or with a curved base to facilitate the mixing of the contents.
4. The stirrer facilitates the even-mixing and oxygen availability throughout the bioreactor.