GENE CLONING:

"The cloning in which identical copies of genes are produced is called gene cloning".

PCR (Polymerase Chain Reaction):

"The reaction which is used for production of lesser number of gene copies within test tube".

While, in case of formation of large gene copies recombinant DNA technology is used.

RECOMBINANT DNA TECHNOLOGY:

Recombinant DNA means a DNA with two different combination of genetic materials. (It is also called Chimeric DNA).

Method for Production of Recombinant DNA:

(i) Interest: Gene of interest (OR) selection, which is used to be cloned.

(ii) Cut out: Scissors enzymes (restriction endonuclease) to cut out the gene of interest.

(iii) Placement: Molecular carrier or VECTOR, on which gene of interest could be placed

(iv) Introduction: The gene of interest along with the vector is then introduced into an expression system, as a result of which a specific product is made.

Three ways to get the gene of interest:

(i) Isolation of gene from the chromosomes.

(ii) Synthesis of gene chemically.

(iii) Making of gene from mRNA.

Procedure:

(i) Isolation by restriction enzyme: The gene of interest can be isolated from the chromosomes by cutting restriction endonuclease is used to cut on the flanking sites of the gene.

(ii) Synthesis of small genes: In case of small genes they can also be synthesized in the laboratory.

(iii) Use of reverse transcriptase: Genes may be synthesized from mRNA by using the reverse transcriptase (an enzyme). This kind of DNA is called complementary DNA i.e, cDNA 

DEFINITIONS

Cloning: 
A technique for developing large numbers of genetically identical cells or organisms is known as cloning.

Recombination:
Formation of a new association of DNA molecules or part of DNA molecules is termed as recombination.

Vector:
A plasmid that carries an inserted pieces of DNA into a host cell in recombinant DNA technology

(OR)

Any DNA molecule, such as plasmid, which serves to carry foreign DNA into host cells, where it may be replicated and expressed.

Gene:
An unit of inheritance is called gene.

Genome:
The total genetic constitution of an organism is known as genome.


Q No.2 Differentiate between restriction endonuclease and ligase?

Restriction Endonuclease (Scissor):
(i) It is the enzyme which can cut a DNA molecule within the strand.
(ii) It is also termed as "scissor".
(iii) "Restriction endonuclease" recognizes specific nucleotide sequence in DNA and then cut both strands in specific manner.

Ligase (Glue):
(i) The enzyme which has ability to seal up the DNA molecule.
(ii) Is is also termed as "glue".
(iii) "Enzyme that creates bonds between the ends of DNA molecules and form a large polynucleotide".

BIOTECHNOLOGY:

"The molecular genetics which enables us to manipulate genetic materials for the welfare of mankind".

Desired varieties are formed by gene recombinations. These recombinant genes are made for the production of substance such as enzymes, antibiotics, and hormones needed for human use.

GENE THERAPY:

"The process by which faulty genes are replaced by normal genes is known as gene therapy".

Genotype and then Phenotype of organisms may be changed for important and good results by gene therapy. "Genetic engineering means manipulation of genes by man"


★ Gene Therapy in Bacteria

Many kinds of useful bacteria have been reproduced by genetic engineering:

(i) Clean up Pollutants: Some genetically engineered bacteria are used to clean up environmental pollutants.

(ii) Increase the Fertility of Soil: Certain bacteria have been engineered which increase the fertility of soil.

(iii) Kill Insects Pests: Bacteria are also used to kill insect pests.

★ Gene Therapy in Man

(i) Medical Applications: These include the production of hormones, vaccines, enzymes, antibodies, antibiotics and vitamins, and the gene therapy for some hereditary diseases.

(ii) Human insulin has been prepared by this method. It plays an important role in treating the diabetic patients.

Genetic engineering is also playing excellent role in industrial applications, environmental applications, agricultural applications and biological researches.